This is the exact same behavior I have noticed from YouTube as well. I miss the "old" YouTube around 2011, when it was a terrific place to discover new and interesting videos. If I watched a video on mountain biking, let's say, then the list of suggested videos all revolved around that topic. But in today's YouTube, the suggested content for the same mountain biking video is all unrelated, often extremely polarizing, political content. I actually can NO LONGER discover new interesting content on YouTube. Like you say, it automatically categorizes you based on the very first few videos and that's all you see from there on out. That is why I have now configured my browser to block all cookies from YouTube. I'm annoyed that I can no longer enjoy YouTube logged in, but at least now I feel like I've gotten back that "old" YouTube of what it once was. It's a whole lot less polarizing now, I feel much better as a result of it, and the suggestions are significantly improved.
Exactly. I remember clicking on homepage to get selection of new, interesting videos. Now I just get exactly the same every time I click. Useless. I would like to discover new topics not get rehash of same ones.