Anyone who has used YouTube enough while logged in probably has noticed how music playlists start looping the same songs and how recommendations start repeating.
I've found that the best method to avoid that is actively reverse train the suggestion "neural net" or whatever they use. Asking friends for video recommendations, refreshing page multiple times when recommendations are all too similar, marking suggestions of known topics as boring, clicking on new topics more than old ones and so on.
It's really rather fascinating how easy it is to fall into a bubble and how hard is it to extend it. I do suspect it works great for most users and that's why it is like that.