Congratulations, you've found fashion. The reason why things were more varied in previous generations is the speed of communications. it took much longer for fashions to permeate through society, this mean that more local variations happened. Now, fashions are almost always global, but they still change at the same rate. The difference being is that they change much more in unison across the globe.
(I've been observing this for at least the past 15 years or so. This feels more like the "post-history" of fashion.)
Edit: Regarding the speed of communications, mind that there were much read, trend-setting magazines, which came out periodically, every week or every month and that they had to make a point, relative to the previous issues. And, as a reader, you wouldn't have referred to a past issue from half a year ago. Moreover, past issues were hard to come upon, as they weren't sold anymore. Now compare this to websites, which keep lingering around (you wouldn't discard last month's posts) and platforms, where trends gradually gain momentum, until they eventually become ubiquitous. (At this point, a trend would have been "out" and "uncool", previously, but now this is when they are really enforced by algorithms.) I'd rather argue, for things like fashion, the speed of communications has decreased considerably and stability has increased, thanks to technology.