Sadly, not anymore - used to be the case quite a while ago, but not today anymore as the ads come from the same domains the videos are streamed from.

Those simpler popover-ads which can be closed clicking an X in the upper right corner still are blocked tho...

Spilling my secret tho (and YouTube execs hate me for it!): i block YouTube in my mind and only rarely go to it if i really need to watch a video (which, for me, is rarer than i ever thought it'd be).