Very overrated, especially since unless you know something about the game he's reviewing before hand, you will not understand anything he's talking about...and if you already had prior knowledge of the game, it was likely because you played it or saw another review, in which case his video is useless.
I'm not going to hold that against him. Generally, people listen for personality and not for objectivity. Listening to someone sperg about a video game you've never heard of is boring and confusing, listening to someone sperg about a video game you're already familiar with is also boring because chances are their take on it is something you already know.
This also affects podcasts hard as well, especially when people talk about movies or TV shows, and describe everything that happens, which you either won't care about it, or already saw the TV show/movie in question.
I should also clarify that "listening for personality" only applies if you're relatively consistent with your content and/or your schedule. The fastest way to lose fans is to slack off on content (while taking Patreon money anyway) and being an abrasive SOB whenever possible. This is where Yahtzee has actually done very well where others have failed. Despite the deteriorating politics-in-videos situation, Yahtzee has done remarkably well with scheduling and consistency.
If you look at fellow ex-coworker Jim Sterling, he was already damaged goods in 2016 as far as personality and character went, it wasn't until he trooned out that his popularity plummeted. (I suspect Jim's in on the Patreon pay-each-other scam, his patrons have more than doubled since
November 2016; compare
current, screenshot below for posterity), but he's making $2k less than he used to. Despite looking completely repulsive and sounding just as bad, I suspect the reason Jim's still afloat is he still turns out content on a regular and consistent basis.
edit: screenshot in question (I use a scriptblocker, that's why it looks weird)