My 4yo DD is utterly obsessed with those YouTube videos where they play with peppa pig toys and the like. I was relatively unbothered about it but saw some freaky stuff in some of them, and then read about ElsaGate, so have been saying they've 'ran out'.
But today for instance, i was on YouTube looking for Christmas songs and cartoons for her and then the weird things just start playing automatically after. So she knows they haven't ran out. I then said they're not very good for your brain but she doesn't really get this.
So I stuck a normal one on and she was placated, but the creepy ones are probably more common than the normal ones! I'm pretty much always in the room with her or in the basically open plan kitchen cooking but they're absolutely mind numbing and if I'm trying to work I don't want to miss something that will scar her forever 
I don't have a real problem with her watching the innocent ones sometimes, some of them are quite creative in the way that they play and she never asks for the things so it's not from a particular consumerist concern - though it does concern me how much she adores them more than anything else on tv - they're like crack to kids! And Elsagate is bloody creepy, I read some seriously disturbing stuff on reddit from this guy that used to work at the place they were produced. Terrible that YouTube aren't taking a firm stance on it.
Don't know whether to just ban YouTube forever, or if YouTube kids actually works to block them? YouTube is pretty good for music (nursery rhymes etc) and obscure Christmas episodes of her favourite cartoons.
Btw she only watches tv for an hour or two on weekend days, an hour in the morning and whilst dinners cooking .. the other 10 are full of outside time and playing with me and her own real toys. Am a LP who unfortunately atm does have to do the odd bit of catching up with emails etc at the weekend. Am pretty relaxed with screen time but she has a good life outside of it all preparing for the inevitable flame