People like different things. There are definitely some things on YouTube that are objectively low quality, but I think the genres/channels you're describing are just things that people other than yourself enjoy. The demographics of YouTube are no doubt different than the demographics of Hacker News.
Maybe food analogy is good? If you put on the table: potato chips and a green salad with grilled chicken which one would most people choose? Could people agree on the definition of "quality" in this case?
