I think what’s different is the absence of one (or few) specific styles being in vogue. Mod, as you mentioned above, or any other subculture/style from the past were very distinctive and would rarely intercept with each other. Something was always in, while everything else wasn’t. And now it is more dependent than ever, in my opinion, on how you present and handle yourself rather than what you decide to wear. Everything is in and nothing’s off limits. Though I’d disagree that everything is homogenous; on the contrary, I see the biggest style variations now, and also much more experimentation among younger people, both online and irl. And that feels way more natural to me than conforming to a fairly strict confines of a certain style (though people like that still exist, obviously).
Though I must admit that, of course, not literally everything works and sometimes you’d end up looking ridiculous. But that’s always been the case.