Good question. I'm also on the lookout for quality content for my kids. I recently learned that YouTube Kids can be put into whitelist-only mode, and that specific channels, videos, or collections of channels can be picked individually. Google aren't making it easy, but the option is there.
> Does YouTube kill those channels?
I don't think it's about YouTube. Mr Beast is good at what he does, and manages to produce very marketable content. It's fast-food entertainment. It's a newer take on what's been on our TV screens for decades in the form of reality TV and game shows.