They still build recommendations even if you’re not logged in, you can see them in the sidebar after you load a video. Imo they only removed them from the homepage to try convincing people to log in or create account, it’s all about increasing user numbers, ad engagement, and data collection these days.

They could give us a list of topics to choose that we’re interested in, it wouldn’t be nearly as accurate as with watch history but it’d be nice to have when watch history is disabled

They can base the recommendations on your subscriptions.