I'd also appreciate if it went back to recommending videos similar to the current video I was on instead of having the same recommendations on every video now.

Or at least keep it in the "watch again" section. I appreciate it from time-to-time for certain music videos and think "sure, I'll listen to that again".

This is a flaw of the fundamental nature of the service. If it were a clientside application, keeping track of your entire viewing history forever would be trivial. But because it's on a remote server, keeping everyones history forever would be very difficult. I would guess they're probably using a bloom filter and just not dedicating enough resources to it per-user. Or, maybe even more likely, they ran 1 experiment 1 time on a few users and discovered that re-watching previously watched content was popular and extrapolated from that - ignoring that their sample size included a great many children (since they outnumber adults) resulting in them just expecting everyone to act like children.

I'd be happy if it didn't recommend the exact same videos two or three times on the same page, but that seems a lot to expect apparently.