I can't believe the sentiment in the comments here.
...Y'all think spammers are going to label themselves as "AI generated" if that's detrimental? They will not, and it's not something that can be objectively detected.
Getting customers to moderate this is self defeating, as the whole point of spam is to get in front of buyers' eyeballs.
Valve needs to hire staff to cull this junk, they can afford to, but they don't want to. That's the crux of the issue.