Engagement metrics fed into recommendations algorithms are the paperclip maximizers that feed humanity's collective poison.
Europe should do the one thing it knows how to do: regulate. For once, it is the answer. Do it only there. The rest of the dominos will fall.
Making a european branded humanity poisoner is not the answer.
Specifically, regulating against silent signals like watch time and comment count. Upvotes/likes can serve a purpose and would not cause the situation we're in now.
We need to get specific about the real issue.
Do you mean regulating "watch time and comment count" at the presentation (to the client) or the server (business/analytics) level? If the later, how would you even enforce that?