Years ago I had found his channel and liked it, and then some video (I don’t remember the title or even subject at this time) came up on a subject I happened to know quite a bit about. He got to some point in an explanation, bungled it, and then hand-waved it away, saying the details were unimportant.

Stopped caring about anything he had to say after that, and I also then realized that there was a an entire genre of “person with no actual expertise reads Wikipedia articles and explains them with good lighting and high production quality.”

Same. It was the "How The U.S. Ruined Bread" video for me after which I started watching critically and found the editing style to be over the top and makes it harder to think about the content while it's being presented. So I eventually stopped watching.