froyo's dominance is pretty much just the inevitable result of an amateur game with a relatively small talent pool.
as others have said, no one can afford (literally) to put in the effort of b4nny consistently, which isn't changing anytime soon. on top of that, an underrated aspect of froyo's dominance is that, as the #1 team, they've always had the ability to get talent from other teams- yomps, arekk and habib were all already on the #2 or #3 teams in invite when b4nny grabbed them up, meaning that a) they were already incredibly strong players and b) he was simultaneously weakening his biggest rivals. I'm not saying there's anything wrong with this, it's just natural.
the difference in a game like, say, CS:GO, is that the number of truly elite players is just too high for such a strat to result in a permanent #1 team. in fact, this sort of thing happens in domestic scenes all the time. SK reached the top by always picking up the best Brazilian players; same with Astralis for Denmark and with Na'Vi for the CIS region. we just don't think of Ascent as being like the Immortals or the North of tf2 because there's only ONE superteam (at least in NA) in this analogy, not 4 or 5.
the sad truth is, this season's ascent roster only had 2-3 individual players at the level of the guys on froyotech, so no amount of practice and dedication could quickly close the gap. I personally feel like there's enough talent in NA to build a team that, like Ascent from a few seasons ago, can get very close to froyo and maybe beat them 10-20% of the time. however, even that team wouldn't be CONSISTENTLY as good, and I don't think there's enough talent to sustain more than one team like that at a time.
tf2 came out in 2007, had no developer support compared to modern games, and still has a small but vibrant and passionate scene compared to most games of its ilk. to me, that's enough, and I've made my peace with dwindling pug playerbases and tiny prize pools. froyo being this dominant is just another consequence of our situation. but you know what? tf2 has had a good run regardless.