Kids aged 2 and 3 should watch any content together with their parent. Or at the very least, the content that parent watched and approved before. No 2 or 3 year old should be mindlessly browsing Youtube
Have a look at Youtube Kids ( https://kids.youtube.com/ )
You can block channels, but there are so many of them that it's a losing battle. I would really rather just whitelist some specific channels, but I haven't yet found a way to do that.
I want to encourage my 2yo to be able to use technology like the tablet (and in fact, it's frightening how good she is at figuring it out) but I also don't want her watching this garbage. If she picks one of these and I turn it off, she gets annoyed at me and doesn't understand. I'd rather be able to let her pick her own show without worrying about exactly what it is, by having things like PBS, Sesame Street, TVO, etc pre-approved.