The only thing I can see that could possibly be done is to either remove commenting altogether, and remove that as a method for determining engagement with the video. Or to make it so that to comment requires full validation (either by restricting to individuals with Youtube Premium, or some cost to be able to comment) of the individual who is commenting so that automation of it is no longer feasible from a monetary perspective. In theory, they could still allow users to post "Anonymously" but they would have to be posting from an account which has been paid for, or for which some monetary or time cost was necessary to prevent a spammer from simply spinning up more accounts.

There is no way to automate this because you have too much money on the side of the scammer should they break through it since if they only catch 1 out of 10,000 people, it immediately pays their bills. This is the big issue with email spam, we can fight and fight, but at the end of the say, there is no monetary cost really to sending out a stupidly absurd number of emails.