On top of that, in my experience both CuriousityStream and Nebula's search functionality is pretty bad: I got fed up of the number of times I searched for something mentioned in a spoken "advertisment" by users like Mustard on youtube who said they have extra content on those services and then I can't find it or find out how to list all videos by those users, I stopped my subscription to them...
I follow a wide variety of channels, but there are maybe a dozen to 20 that I would consider essential. Maybe 3-4 are on Nebula.
I think for a lot of viewers and creators, YouTube is simply inevitable at this point.