I curate content for my five year old daughter, and she can easily browse it, without descending into the rabbit hole that is YouTube-at-large. It's easy for me to do, but only because my main project (https://pianop.ly/) involves embedding YouTube videos into web pages, and I have a ton of tools that make it easy (for me, not necessarily for anyone).
I don't understand why there isn't more of this. I wish there was a large community of parents that wanted to curate content -- educational, musical, etc -- that kids could enjoy without parents having to worry so much they'll either stumble into truly awful stuff, or more likely, just spend their time looking at completely inane timewasters. (opening eggs to reveal toys, etc)
A side benefit is that if a video is embedded into a web page, the only ads YouTube ever shows is a banner. (although, I pay $10 a month to have YouTube without ads, so that isn't an issue for me. We don't have Netflix or cable or broadcast TV, by the way)
Incidentally, my daughter and I have friends (another dad and daughter) that are YouTubers, and while this girl is only 8, their content is good (in my opinion) and is a creative outlet for them and they have a lot of fun with it. The dad is an excellent videographer/editor, and the daughter is an excellent skateboarder, and they combine those things and share it with the world. (we met via YouTube and the four of us meet up at skateparks...my daughter is also really good) https://www.youtube.com/watch?v=wzrrgcqyvF4 I just don't see the problem with this.