I suppose I should clarify my position a little more: I don't have a problem with Ubers in this meta. I make use of a few myself to great effect and I think they add great flavor to the meta without completely defining it (well...MOSTLY, but we'll get back to that). Shared Power as a meta is defined by its momentum, where having strong checks and counters are necessary if you want to win. If your opponent is hyper offensive, you need a good revenge killer to stop it from sweeping. If the opponent is stall, you need something that can go nova on it to prevent it from recovering all its health with Sitrus Berry + Ripen + Cheek Pounch. The problem I am seeing is that many players can just skip the game of checks and balances by slapping a Scarf on two or three high-damage Pokémon and see a significant degree of success. Legendaries are typically at the forefront of the problem, given their huge BSTs and solid move pools, but I think the crux of the problem lies in the speed control of the meta.I want to bring up a point you might be missing and that is the bulk that Uber/Legendary pokemon provide.
Take a look at the list you stated, then go look at finnegans berry team with giratina, vnmmz teams he listed giratina, palkia, dialga, terapagos, Byleths team with zamazenta, solegaleo, my angershell team spamming ubers pokemon, Bobs classic stall with giratina, InkyDarkBirds regenerator stall with HoOh, Ballz number 1 teams with arceus, giratina, and fluttermane. All of these teams that hit the top 25 all use at least 1 if not more legendaries/uber pokemon. These pokemon all play an extremely pivotal part of the team and are not just donors. For the most part they are the answer to the opponent's strongest pokemon likely another legendary/uber because they can take multiple hits with very little defensive investment and dish out crazy damage with no setup. Just putting this out there it might be an interesting shake up to ban all ubers and allow testing on others.
Just to bring in a bit of data that I have from playing all of you using the same data I collected from my adaptability post. My average win rate is 70.1% over this collection period of 3-4 months my average ranking over this time was 1419 highest being 1677 and lowest 1192 during this time, logging a total of 930 games.
The worst performing uber pokemon that I have played against is roaring moon with a 10% win rate in 10 games and the best performing uber is Palkia-Origin at 83.3% winrate in only 6 games. The best and worst win rates with over 30 games played against are Arceus-Dragon with 56.7% win rate in the top 6 and ursa luna-blood moon at 26.7% win rate bottom 3. The most used uber in the meta is Giratina-Origin with a win rate of 42.3% with 97 battles against it. The average win rate against me for an uber ranked pokemon is 40.57%. In general putting an uber level pokemon on your team increases your win rate significantly roughly 10% for people playing against me. They are just that good even if they are not donating a good ability in the case of palkia, and arceus.
Outside of stall teams (mostly, but again, we're getting there), this meta is all about speed. Scarf, Sash to survive being outsped, priority, super priority, super DUPER priority, speed control is essential to winning consistently for most teams here, which is why Scarf spam is so prevalent. The shared power (tee hee) of your abilities lets your team bypass power limits, and the Scarf lets you bypass speed limits. Unless you are specifically running stall team abilities, almost no Pokémon in the meta will survive a hit from a Steely Spirit + Adaptability + Sand Force Sunsteel Strike from Solgalio, and thanks to Scarf, next to no Pokémon can revenge KO it, unless they have a good type advantage (something further complicated by Tera). It essentially forces the opponent to sacrifice 2 Pokémon to beat it, and if you've got 3 Pokémon with that kinda power on your team, it's just a numbers game at that point. I think limiting the Choice Scarf item would largely remedy this problem, as it now means players have to actually play the speed control game of the meta, rather than bypassing it.
That being said, I think there's one uber Pokémon that absolutely DOES deserve a ban. It's time I finally address the elephant in the room...or rather the dire wolf.
Zamazenta. This stupid, ridiculous Pokémon. Bulk that makes the best stallers envious (helped even further by ally abilities like Fluffy or Vessel of Ruin), one of the best unrestricted abilities in the entire meta, able to setup sweep using its defensive stat, but the best part, OH the best part, is that Zamazenta is the 4th fastest Pokémon in the entire meta, outsped only by Dragapult, Electrode, and Deoxys. That's absurd. How on earth has this Pokémon NOT been banned yet? Even potential counters like Booster Energy Iron Valiant and Flutter Mane or Specs Draco Meteor Dragapult aren't reliable thanks to Tera-Steel. Zamazenta is an absolute terror in this meta, and I think it has MORE than demonstrated why it should be considered for removal from Shared Power.