This will kind of clean up your current recommendations but it doesn't reset the recommendation algorithm like it used to. The algorithm still retains memory of your past behaviour.

For example if I consistently listen to 3 unrelated songs [A B C] on youtube together, the algorithm will regularly recommend them to me (because of my unique behaviour, not because they're similar). If I reset my history and then listen to song A, then B and C get immediately recommended even though they aren't similar to A and they don't exist in my listening history which means that the information about my listening/browsing habits is still there in the recommendation model.

If you turn off watch history is basically only suggests stuff based on subscriptions which is much better imo and I never need the history feature anyway.

I never log into YouTube and this still happens, it's at least in part keyed to IP address