Once upon a time, feminism was a pretty good idea. Women were oppressed. Women were considered inferior to men, by everyone, and were treated badly. Women were mistreated a bit like children still are. They couldn't vote, they couldn't work in most jobs, and no one expected them to have good ideas. In any disagreement between a man and a women or child, the man was presumed correct.
Men could intimidate their wife and children. And even hit them. Obedience was expected. Even the legal system was unfair. Up until 1993, some U.S. states had special exceptions in rape laws so that raping your wife wasn't a crime.
Eventually, feminism won (in the U.S. but not in Iran). Not 100%, but pretty close. Women are no longer an especially notable victim group. The situation (in the West) isn't perfect, but there are lots of other things that are worse (like the treatment of children or the "mentally ill"). The treatment of women, by society, doesn't stand out. Women are no longer oppressed, much.
Lacking oppression to criticize, feminists today complain about non-problems like the fictitious campus rape epidemic. They created this "problem" by saying if a women regrets sex later, or had one beer, then it's rape. And they put a lot of money towards encouraging females to come forward with rape accusations along those lines.
Women can vote. Women can be top executives or scientists or politicians. It's hard for feminists to find legitimate things to complain about. Women aren't being externally oppressed.
Feminists claim women are paid less for doing the same job. But they compare different jobs. For example, a women who takes time off from work to have a baby isn't offering the same services to her employer that a typical man would. 2.3 lengthy vacations (which the employer may or may not have to pay for) make her service less valuable (due to having to hire and train a part-time replacement, or other downsides). Another difference is that women, on average, put less effort into negotiating for a higher salary. In that case, a company which pays people partly according to their salary negotiation efforts would pay women less. Whether that's a good system or not, it's pretty common and is applied equally to men and to women.
Not everything is equal, but feminists don't want to address the main remaining issues. No longer are women particularly oppressed by men or by society. But women are often more passive, less persistent/tough/responsible, more emotional, worse at negotiating, worse at math, and have worse job skills. And plenty more. Why?
Some people believe women are genetically inferior (as a matter of unfortunate scientific fact, not sexism). I'm not going to argue about that topic here, but I will say I don't believe genetics are the issue. I think it's a cultural issue.
A big part of the issue is women, on average in aggregate, have different priorities than men. They put more effort towards parenting, socializing and appearance. They place a higher value on emotional sensitivity, tact and certain kinds of relationships. What feminists don't want to face is that you can't have it both ways. Neither men nor women have the magic ability to be really good at everything. Lots of women are worse at math because they put less effort into being good at math, preferring other skills instead. Lots of women have worse careers than men because they put more effort into other things besides their career. That isn't oppression, it's choice.
Another part of the issue is that women are encouraged, at a young age, primarily by their mothers, to pursue a female-appropriate lifestyle (e.g. not math). Men are also encouraged, at a young age, to pursue a male-appropriate lifestyle. Everyone is under tremendous social pressure to conform to gender roles. This is primarily from first their parents and early teachers, and then themselves and their peers. It's not enforced by the authorities, by business, by scientific leaders, by university teachers, or by men. Feminists aren't very happy with this perspective because it's not the fault or men or authorities. It's the fault of everyone pretty equally including all the women, and it hurts men too.
Women can be, and often are, oppressors of little girls. Women especially are the oppressors here because they are more often the active parents and teachers of young children. This is not compatible with feminist blame-men-as-oppressors ideology.
If a women deviates from her social role, she'll be punished socially. People won't like her or want to date and marry her. But that's basically it. There's no real oppression of women. The same thing happens to men, they're also socially punished for role deviation. That's bad in both cases, but it's not what feminism is about.
The gender roles in our culture are not equal, feminism doesn't want to take a frank look at them and how to change them. Instead, it blames men. It's criticized a lot of flaws of the male gender role. And it's had a lot of success. Men have changed, the male gender role has improved. Result? Men are now better than women. Feminism helped men improve while shielding women from the criticism that could be the source of their own progress. And feminism doesn't want to take on gender roles themselves in a serious way because it's committed to defending some amount of feminine behavior as non-bad.
Feminists want to retain lots of the female social role and then blame the consequences in reality on oppression by others. Ideas have consequences, living particular lifestyles has consequences. Women aren't paid less for being women, they are paid less for living a lifestyle that's less productive and assertive in terms of career. (There are always exceptions. Some individuals are sexist. But most people find sexism offensive and horrible.)
Feminism wants a lot of special treatment for women. Women can follow their gendered role of dressing up sexy, but then if a man follows his gendered role of how to respond to sexy outfits, he might be accused of sexual harassment. Feminists want women to have this weird hybrid of reason and femininity, in whatever way their whims decide, while men aren't allowed to do an arbitrary hybrid of reason and irrational masculinity. They don't blame the woman for initiating and participating in that gender role interaction by dressing sexy. Instead they pretty much set things up so the women has, at her whim, the choice to name you an attractive suitor she wants to date, or a harasser she wants to sue. She can do this in response to identical behavior just because of a man's appearance, with no regard for the fact that the "harasser" was just doing normal courtship behavior like everyone else, male or female.
There is also such thing as real harassment, which is different, and not especially common. Many of the worst cases I read people yelling about involve a woman encouraging lots of it, playing along in lots of ways, never being clear to stop, then complaining later. Note that statements like "omfg stop" are things women often do as part of flirting, they are not clear communications to stop. If you really want to tell a guy to stop, you need to be clearer than that. For example, use a cold tone of voice and boring repetitive language. If you say, "Stop, I do not consent, I want you to stop" in a monotone voice, several times, people are going to realize this is not in good fun. If you squeal "omfg stop, what if we get caught? no no you can't do that, omg, this is so intense" then that isn't actually telling him to stop.
Lots of women routinely say a half-hearted "no" in order to avoid responsibility (in their own minds, not in fact) for what happens next. In that context, actually saying no requires substantial clarity. Saying "no" should be a clear confrontation, if it really means "no". Many women try to avoid confrontation by saying "no" in unclear ways that won't offend anyone, then later say "well i told him no! he abused me!". If you aren't willing to say "no" in a confrontational way, you played along. Bullshit harassment claims are a big problem.
Anyway, gender roles often conflict with reason. Feminists selectively use reason to criticize when men pursue gender roles contrary to reason, but not when women do. They want men to change, but women don't have to change. This is sexist against women. Why shouldn't women make changes to improve? Why should they be told they are fine the way they are, and don't worry about changing? Feminists are now on the side of preventing the progress of women by saying women aren't ever to blame for anything bad.\
Feminism identified external oppression as the problem women face. 200 years ago, there was a lot of truth to that. There was a lot of oppression of women. Today, there isn't much oppression of women. And it turns out, oppression was never the whole problem. The female gender role has plenty of problems that have nothing to do with oppression. So feminism is trying to solve the wrong problem while actually denying the real problem exists. Feminism is now part of the problem.
The male gender role also had lots of flaws. However, feminism had a lot of success pointing out some of those flaws. So feminism managed to improve the male gender role. It still has flaws, but less so.
Big picture, the feminists complained about men and got them to reform a lot (not completely). So, feminists helped men improve. Meanwhile feminists did not help women improve. The results is men are now, on average in aggregate, better people than women. Long ago everyone sucked. Now men have improved a lot (thanks partly to helpful feminists), but women keep saying they don't need to change anything, they want reality (and men) to do all the changing to improve the lives of women. That is a big mistake.
So to summarize, feminism criticized some problems with men. Thanks to the helpful criticism, men improved. Meanwhile feminism denied women have flaws and should make any changes. Then feminism is mad that men are now better than women. (What did they expect? Criticism is helpful. Encouraging people to see themselves as helpless victims is not helpful.)
Feminism demanded more responsibility from men, and less obedience to their flawed gender role. But for women, feminism defends their irresponsible obedience to their own gender role. (With superficial exceptions like feminists often dislike makeup, which they incorrectly blame on men.)
Feminism got men to be less like assholes and reduce some other flaws. It meant to help women. This did help women some. But it helped men more. Men being assholes was worse for men than it was for women. Feminism doesn't understand.