Besides the obvious lack of advertisements, most my the improvements would come from resolving my main issue with YouTube, which is how aggressively the service directs you towards content with ads. I feel that this was not the case many years ago and that YouTube has actually gone backwards in terms of having a reasonable interface for navigating through the vast amount of information it hosts. I feel channels, suggested videos, subscriptions, searching, and even monetization were more user-friendly back in the early 10's.

The problem is that, as far as I know, YouTube has not been wholly profitable for Google at this point, so they've really been trying to squeeze all the money they can out of it, and I feel it's come at the expense of the service itself. I spend far less time on YouTube these days.

I would be much happier spending money directly on a service which treated its users as customers rather than the product.

As far as other features, I think it's naive to say that YouTube has every feature someone could want a video hosting service to have. I feel YouTube could improve quite a bit in plenty of areas, particularly in how people 'watch' music there.