Exactly this; TikTok has careful moderation and curation within specific styles and a (relative simple) algorithm to quickly figure what the user is interested

Exactly this; TikTok has careful moderation and curation within specific styles and a (relative simple) algorithm to quickly figure what the user is interested in. Plus a lot less advertisement. That is their "innovation"; and is also something that is hard for YouTube and Instagram to copy as it would mean they would have to spend more and monetize less.