Feminism is equal rights and opportunities for everyone. My added thing is equal responsibilities. This is the dictionary type of definition.

Most people (at least the vocal ones) are either completely sexist (both sides - feminazis and sexist men) or think it is only about promoting interests of women.

I can’t give you all the possible views off the top of my head but I'll try.

1. If you are not a feminist, you are sexist. - There is no nuance or leniency for human nature. This makes skeptics jump to opposition because they feel attacked for their behaviour. Any further push only makes them more apprehensive.
2. Men have it so good - This is kind of a mixed bag for even me because it is situation and topic specific. Men have had better opportunities for some things like education or jobs, yes. But they have fared worse in some other things like emotions, expectations, dating, etc. Now, if someone who struggles with a lot of things is told "Men have it so much better", they will not agree because any one person can only experience their own problems. On the other hand, there are men who feel women have it too easy with how they can earn money by selling porn, they can get out of situations by crying, how easy it is for women to get laid, etc. I don’t necessarily agree with everything but this is what I have seen people say. So, this makes "Men have it better" laughable for some people.
3. Where are the equal responsibilities? - Feminism promotes equal rights but (conveniently) ignore the equal responsibilities part. A lot of women like to be damsels in distress and also want to enjoy the perks of freedom and equality. This is something I personally despise a lot.