Why do so many men try to make their personal issues about the opposite sex?

I have a guess: it's hard for insecure people to be critical of their own personality and/or behavior without hating themselves, so they don't reflect on their behavior and then end up villainizing the opposite sex for triggering their insecurities.

Dudes who just got money will be like "omg, women pay so much more attention to me now. They're so shallow." No, you just failed to attract them in other ways before having money. That's on you, not them. You didn't discover a secret truth about women; you failed to look deep into your own experiences. Poor dudes still get laid. Just go to a dive bar sometime.

Same with dudes who get muscles and complain women only want muscles. They don't only want muscles; you just didn't attract any without them. Skinny dudes still get laid. In fact, many women assume muscular men are insecure and some find it gross.

My experience is women care more about personality than any of the things men get insecure about, and women like a larger variety of men than insecure men imagine they do; but men with shitty/no personalities who think they have good ones won't realize that. But it's telling that their personality isn't good because instead of asking "why did I fail to attract women without x thing?" they instead try to argue that women in general only want x thing and get bitter about it.

Women aren't a monolith. Your bad experiences are not an insight into some kind of underlying collective female nature you imagine they have. Look within.