unpopular opinion: I think what @TeamYouTube is doing with thumbnails isn't a big deal - websites do A/B testing all the time, they want to determine whether auto-generated thumbnails lead to higher click rates, which would actually be beneficial to channels, not "killing" them
I see what you're saying, but I think they easily could've gotten 0.3% of their userbase to AGREE to opting into a test like that. I think people are angry that Youtube has explicitly tampered with people's content WITHOUT their permission.