YouTube Has NO Spam Filter

I'm starting to suspect that YouTube doesn't have any autochecks for spam at all. I mean really, they don't have a program checking if the same user is resendinh the same exact string of characters over and over again? At this point I want to know WHY. This goes beyond laziness and lack of caring or difficulties managing the same amount, or even overload with reviews. Their automoderation clearly isn't even checking for repeated messages of the same exact string of characters, from the same account - this seems like it should be ridiculously easy to check for, and one of the first defenses implemented against spam. So what's going on? Does anyone even actually know? Not merely memes about YouTube not caring, but what's genuinely going on from YouTube's side?