But that's the real problem. You can't just average everyone and apply that result to anyone. The "average of everyone" fits exactly NO ONE.
The US Navy figured this out long ago in a famous anecdote in fact. They wanted to fit a cockpit to the "average" pilot, took a shitload of measurements of a lot of airmen, and it ended up nobody fit.
The actual solution was customization and accommodations.
There isn't even an "I've watched this" or "don't suggest this video anymore" option. You can only say "I'm not interested" which I don't want to do because it will seems like it will downrank the entire channel.
Even if that is the case, I rarely watch the same video, so the recommendation engine should be able to pick that up.