I want to talk more about the mons in question; as far as Chien goes, its cool and all to to look at game by game examples, but builder restrictions should and do matter as far as broken mons go.
Matchups like flying, poison, dragon, mirror, all of these are just 1 uncomfortable turn away from either chien winning or chien opening a big hole causing smth else to win. Its a near guaranteed high-value button. Even in its more mediocre matchups it has a super controlling presence, it becomes steels biggest hurdle when trying to beat dark with like low kick gambit, rain can just lose to fangs+sucker, and ground is forced to always have bpress quag. Aforementioned dragon also I feel goes from near unviable to just straight up solid w/o chien dark in the mix. Some of these middling checks like corv and quag are also just one crash flinch fish on a recover away from a loss as well.
You have to ask, what are the pros and cons of keeping certain pokemon in the tier. As far as Chien goes the pros end at "it looks cool", and its negatives are making a handful of matchups just the most uncomfy awkward experiences to play out. Unfun to build for, unfun to face, provides little benefit to the tier.
You can extend this train of thought further to other fellow ubers from spectrier, to flutter, to zama, to urshifu, or even guys like kingambit where all of these pokemon do more harm than good. Tour results are a fine metric but each game-by-game isn't going to show the full picture of what is wrong with the metagame.
I am not here trying to say we need to mass ban shit, but quick suspects to get some kind of ball rolling is always good for a tiers health. Every other official tier is very quick on the uptake, noticeably moreso than monotype. I know I am 100% not the only one to share the sentiment that this metagame is just playable at best, and just boring/bad at worst. Stuff needs to change and just staring at weekly winrates instead of acting on how the community feels about certain mons currently in the tier will just make this a slow painful process.