I thought about the AI pollution and I don't think it will matter because we already had the exact same problem with forum spam and low information / bad people (=eternal september) type content overwhelming online discourse.
I think maybe combatting AI spam will be the least of our problems because humans do plenty of AI-tier spam already. I think the advent of AI may even be positive because people will start to value real human interaction more. It will be like a treasure cove when you find a forum that is highly curated with real people and you can rely on that being the case.
Or (and this is just as likely): Online platforms will go towards requiring real human IDs for participants. AI spam would only be used by companies and advertisers.
Maybe eventually there will be a public understanding that only a foolish child would read a reddit frontpage and expect human content. It will all be auto generated to trap people, like a gatcha game.