Treantmonk, Colby, Pack Tactics, even Dungeon Dudes. Whatever you may think of any of them, I'm pretty confident saying they know what they're talking about.
When I said to give me an example, I actually wanted someone who claims Monks are weak in tier 4 like you are. I did not find that from the people we mention.
go back and relook at those, I don't think any of them claimed a high-level Monk was weak. Most of the youtubers evaluate it in general, not level-by-level or specifically in tier 4. If you are talking from level 1-20 Monk is the weakest class, if you are talking about level 16-20 it is the strongest non-caster.
Also Treantmonk specifically says he does not weight high level features in his ratings because most people do not play at those levels.
Edit some additional detail since I looked at the people you mentioned:
Treantmonk: Treantmonk rating of Monks like I said is specifically not focused on high level abilities. Furthermore one of the big issues he speaks of is a lack of ki and the very limited use of their ki features, but this is not a problem in tier 4.
Colby: I can't find a review of the Monk class from Colby, I did find lots of subclass and multiclass builds though and I also got this snippet -
"As much as I and others like to bemoan the relative underpoweredness of the Monk they do get a bunch of stuff that is useful and cool that doesn't show up on the spreadhsheet .... they do suffer from scaling and damage issues, but maybe we should not discount all the super cool and useful features they get so much"
Pack Tactics: Again could not find a video reviewing Monk overall as a class but he said on one of his videos
"I used to believe Monks were the worst, but I have changed my mind" followed with on another video
"we ignore Flurry of Blows because it is a trap"
Dungeon Dudes: I browsed their review from 7 years agon and I did not see anything in there saying or even suggesting they were weak in tier 4. I did not listen to the whole thing because it is too lopng. I did find a couple of exerps though:
"The are fast, they are fierce and they are dangerous .... a Monk can pretty much go anywhere, be anywhere on the battlefield ..."