Actually, TikTok seems to do a good job. They understand they have a lot of children on the app and they take that very seriously as a responsibility. Unfortunately their solution is over-the-top censorship but it works better than other platforms from what I've seen. They used to have a "no politics" policy where TikTok simply wasn't a place for politics. They scale moderation by simply over-moderating and that is in line with their offering of a curated feed as opposed to a "platform" for arbitrary content delivery.