I think the advancement of LLMs, which culminated in the creation of ChatGPT, is this generation's Eternal September. In a couple of decades, we'll talk about how the internet "used to be" before free, public websites were abandoned because our CAPTCHAs could no longer filter out bots and device attestation and continuous mictopayments became the only way to keep platforms spam free.
Even when Microsoft and OpenAI stop hemorrhaging money by giving away stuff like ChatGPT for basically free, the spam farms will run this stuff on their own soon. I expect a wave of internet users to get upset and call paying for used services "enshittification", because people don't realise how much running these AI models actually costs.
I think this will also start the transition of not only AI being sold like Netflix or like mobile data caps, but also to an "every company that doesn't get the most expensive AI will start lagging behind" economy. After all, AI only needs to cost a little less than the manpower it's replacing. Any internet facing company needs good AI to outwit the AI trying to abuse cheap or free services (like trials) that they may offer.
We're probably lucky that AI spammers haven't discovered the Fediverse yet, but if the Fediverse does actually become big enough for mainstream use, we'll see Twitter level reaction spam in no time, and no amount of CAPTCHAs will be able to stop it.