YouTube recommendations have been improving, and I do find a lot of material of interest, which says something as my interests are obscure.

But, and this is a big but: YouTube doesn't provide the options to either dismiss any given suggestion, nor to block specific channels. There's sufficient crap on YouTube that both are essential. I've been campaigning for both features for some time now.

Google's recently implemented an account-wide blocked-users manager. It applies now to G+ and Hangouts, though it may move beyond that. "Google doesn't comment on future plans", as they're fond of saying. I have hopes.