I guess a lot of people must be using YouTube in a different way to how we do. We do allow our 8-year-old to sometimes watch YouTube, after the homework is finished or if sick.
What does he watch? Things like....
* 40-50 year old Russian language cartoons, to help with his language learning.
* Quite a few British shows like Edwardian Farm[1], Victorian Farm[2] and Wartime Farm. Pretty educational stuff.
* Documentaries about stuff he's interested in. At one point it was Nelson's flagship, HMS Victory, another time it was the Cutty Sark[3]. He went through a real tall ships period. We followed this up last summer by visiting both the Victory in Portsmouth and the Cutty Sark in London. It was amazing the way he was able to point things out on the real ships, because he'd watched the documentaries.
* Ski racing. He's mad for it. Races himself on weekends and obsesses with who is winning the World Cup races. Mikaela Shiffrin hitting the record was a big moment.
We never see any adverts on there. I don't know why, maybe something to do with a combination of uBlock Origin and Linux.
We do have a Netflix subscription, because I enjoy watching a few shows on there, but we've never watched anything in the Kids section, because it's 95% crap.
So from our perspective, YouTube is quite a reasonable educational tool, when used under supervision and in moderation.
Edit: I forgot the Australian stuff we watch together! Bush Tucker Man[4] and Fishing the Wild[5] are two worth mentioning.
[1] https://en.wikipedia.org/wiki/Edwardian_Farm
[2] https://en.wikipedia.org/wiki/Victorian_Farm
[3] https://en.wikipedia.org/wiki/Cutty_Sark
[4] https://www.youtube.com/watch?v=lcsZHOD9P8E&list=PL7HSPnTFVA...
[5] https://www.youtube.com/watch?v=v1xGBPQlH_A&list=PLvP8XBCt3L...