As I said, Bazaar I think is something else. Although I agree with @Smmenen that it never had results to warrant restriction, I believe it's because you have to dedicate hate towards it. The CA Bazaar generates in unsurmountable in any aspect. Steven himself once theorised that one way to evaluate a card's power is to count how many zone changes it provides (for example, Ancestral Recall is 3 zone changes from library to hand, etc). Count what Bazaar does in 1 activation and you'll see how it's bizarrely broken. I wouldn't be against restricting it because I don't think it keeps anything in place. It's just a monster we're used to dealing with. I have no formed opinion on whether I personally would restrict or not, but I see merit in discussing it, while I don't see merit in doing that for Shops.
OK so with GGT restricted Bazaar puts 2 Stinkweed Imp into your hand then back into your graveyard, and you discard a card which is favorable in the very early game but unfavorable as the game goes on. So the only clearly favorable zone change is that you mill 10 cards. Of those 10, you're looking at about 4 that actually do something meaningful from the graveyard (i.e. free creatures and spells). So Bazaar "draws" 4 useful cards per turn but you start with 0 useful cards in the graveyard and on average something like 3 useful cards in hand, and Bazaar doesn't advance your board state until the second activation, and even then there's some inconsistency in terms of hitting dredgers.
So by the end of Turn 2, you should have something like 3ish useful cards in hand (or played from hand) and 6ish useful cards from the graveyard. That puts you one card ahead of a deck with literally no ability to generate advantage, and most Vintage decks do not fall in that camp. By the end of Turn 3 you should have something like 15 useful cards in all zones, which is certainly good but on the other hand the countermeasures available to fight this whole deal are roughly a million times stronger than anything available to fight any other strategy. I think a Vintage deck getting a strong advantage by about Turn 3 if the opponent can't find any counterplay (when many strong options exist, including the simple Wasteland) is pretty fair by Vintage standards.
I think there's a Catch-22 here. Belcher won an event. If it was a "good" deck (high expected match win %) the format is broken because Belcher is fast and it's undesirable for fast decks to be "good". If it was a "bad" deck (low expected match win%) the format is broken because this bad deck got lucky, and it's undesirable for players to be subjected to variance in which a bad deck might sometimes just get lucky. Is that an accurate summary of what's already been said?
Based on what I collected before, Dredge was killing at 27% by the end of turn 2, and 60% by turn 3. Effectively would be less than that. So Dredge "effectively" decides its games very quickly.
I'm a little skeptical about that. Most Dredge lists I've seen recently did not have a Dread Return target that gave haste or did direct damage, so the Turn 2 kill % should be zero for such lists.
None of the lists on Goldfish's metagame right now have a haste or direct damage target: https://www.mtggoldfish.com/archetype/vintage-wubg-96200#paper
Even if you're right that Dredge is "effectively" killing on a very early turn (which I think is a fair claim if you're just saying in an abstract way that Dredge is faster than most blue control decks), I think Dredge is scoring kills more slowly than it typically has in the past, which raises the question of why a restriction due to speed would take place now.