I agree with everything you said, and so I started reading comments to judge if a video is good. But the comments are always positive, even when the video is terrible! Like, bad tutorial video, unoriginal pop science video, lame interview with a bored celebrity, the comments are still always positive. Once I saw a comment that said something like "This was a really cool video! <url dot-com>" and I realized the algorithm is suppressing negative comments and promoting positive ones based on words used.