I've noticed this as well, the algorithm hones in on a few topics and videos. Interestingly enough, so does the algorithm on the Quora app. I hate this behavior, I want to use a recommendation algorithm to discover new similar content. My guess is that a "new similar content" algorithm doesn't get the same levels of engagement. Maybe its the same as radio stations playing the same twenty songs on a loop.

Clearly google knows what their doing, its just disheartening that this algorithm is the best for engagement. Also makes me wonder about human habit and reinforcement...