You're too focused on flash. What about sound defense. For example, how often do sweeps work today? Much less often. The game is different. If you can't see it, and refuse to hear that it may be, then that's on you. Keep an open mind is all I'd say when watching BJJ of the past and now.
How often did sweeps work a decade ago? The game is the same. The real improvements have been in terms of training and gyms. It makes it much easier for fighters to learn additional skills and be more well rounded when they have a wrestling coach, BJJ coach, striking coach, nutritionist, strength coach, cardio/agility coach, etc. all in one place.
This does not mean an evolution in the sport or a bunch of new techniques. It just raises the average skill levels of the fighters. The elite guys were already doing this many years ago.
Speaking of BJJ specifically, you think a black belt today is significantly better than a Royce Gracie or equivalent? I call bullshit.