The internet is incomprehensibly vast. Yes, there might be a copy (or multiple copies) of a video you made in your youth on the internet. But as long as it isn't a) prominently available and b) attached to your name, you might be OK.

The situation we have today does allow you to address such a problem: Google can remove search results. It's not possible to do that on the blockchain.

The blockchain is vast and growing. Discovery is difficult.

Google prevents new searches or tries to but if you have the link you can visit without google. Same as the blockchain you would need to know where to look.

But still you can try making it harder to access by cutting the major distribution channels, which perhaps will significantly reduce its propagation velocity. With whatever technologies that refuse to fix this issue, you cannot. This is a critical difference for law enforcement.

You wouldn't stop a torrent. Why should the blockchain be different Discovery still happens elsewhere.

You can't 100% undo it, but you can criminalize distribution. Uploading it to a system from which it cannot be deleted guarantees no leniency.