Context · YouTube
YouTube does not show your child what is best for them, it shows what keeps them watching longest, and those are very different things.
How it works
YouTube measures success in watch time, and every recommendation maximizes the chance that you keep watching, which is why emotionally provocative content gets recommended more, because it is stickier.
What your child experiences
They start with a cooking video and end up watching conspiracy theories, and the algorithm does not intend the destination, it just follows engagement signals.
What to watch for
Watch what they are watching after twenty minutes instead of at the start, because the starting video is usually fine, and it is where the algorithm takes them that actually matters.