I don’t speak for all feminists, but this is how I understand it.
Feminism is a school of thought that claims women are equal and should be treated as equals in regards to power. That sounds OK, right? Feminism seeks to specifically address instances where women are not treated equally for structural reasons, which is a reasonable project to undertake. There are many schools of feminism and the only thing that could be said to be common is that feminists reckon women should be equal to men.
Did you know that someone can be equal, but different? An example might be that female bodies have different requirements to male bodies, and individual people of all kinds are different. Equal, but different. Furthermore, feminism isn’t supposed to run about correcting all issues of male inequality, because feminism specialises. The disadvantaged do not make it their life’s work to fight for the advantaged. That would be nonsensical. Specialising is useful and practical. If you specialise that does not mean you are necessarily single issue and it doesn’t mean you deny the relevance of other claims. You can specialise and have an awareness of intersection, you can consider solidarity as well. But feminism is a historical movement specialising in one thing: correcting the structural issues that undermine female equality.
Feminism is not: hating men, trying to be more powerful than men, trying to harm men. When you talk about feminism, try to understand there are schools of thought that differ in a great deal of ways beyond these basic tenants. If you say something like “Feminism is bullshit” you are actually saying “I don’t think females should be equal.” Know that.