I've said it before, the top players and the fanbase are at odds. Top players desire stagnation, minimization of risk, new techs, and other things along that line, because they want to win. The fans want new stuff, new matchups, new stages, because it makes us hype. So while some top level players are willing to look at what can be done to expand the meta, most are pretty good with their wins, and don't want that to change with new things.
Man these conspiracy theories about how all top players want is meta stagnation so they can keep winning are hilarious.
Also after looking into UCT I really think it shouldn't be legal.
The main issue is that the timer for when platforms appear is inconsistent (can appear like 5-10 seconds earlier/later than expected), and the next round of platforms that appears is random. You can be hit off-stage and walk-offs can appear giving you a free recovery, or you can be spiked into a newly appearing platform below the stage, or you can be getting juggled and have the high platforms above the stage appear giving you a new landing option to escape pressure.
This wouldn't necessarily be an issue if it was predictable (based off the background like Lylat cruise) which platform layout appears next, but there isn't actually any of that, so the reward of your edgeguards, juggles, spikes, etc. is random, and inconsistent rewards like that get a stage banned. It's pretty similar to Brawl Pictochat which was an awful competitive stage, just not to the same degree of awfulness as that.
You can play on UCT and not really notice any issues, because most of the time the platforms aren't
that impactful, but if it remains legal those situations will definitely crop up and people will complain.