At least 95% of what I watch on Youtube is educational or technical. It's self-teaching material, math, science, that sort of thing. Most people would find it dry but I enjoy it.
Still, I wouldn't call it entertainment.
I assure you it has just as many ads: pre-roll ads, clickable ads below the fold, interstitial ads, and "a word from our sponsor" ads as everything else on YouTube.
I suppose I'd still classify it as entertainment even if you paid for YouTube premium.
If we call all content that we enjoy watching “entertainment”, then IMO the word loses the meaning a little.
It’s becoming hard to even find a youtube video that doesn’t have “like and subscribe” somewhere in it, even if it’s not otherwise sponsored.
Most of what I spend my time on on the web and YouTube is more towards educational than entertainment, though the line gets blurry (which is the point of having a unifying term like "content") when it comes to videos about music-making and stuff like that.
If the "content" isn't entertainment, it often has no ads and is referred to via another name.