I personally think AI has less of an effect on the tumultuous changes the web is going through. I think it's really only the cherry on top, and the biggest cause IMO is the "infinite growth at the cost of infinite debt free and powered by ads paying 1/1000 of a $ per view" model collapsing.
Sure AI putting out sludge content and using up server space might not be helping, but the web already might be fracturing and IMO it could turn out alright. A static blog can be hosted for free or extremely cheap, a small hosted community like a fediverse instance can be hosted for 3-5$, and more competition amongst the corporate sites (Facebook, Twitter, YouTube) is not a bad thing - and bonus points if people start following content from those services from within web wrappers or RSS instead of the official apps.
And yeah, it wouldn't be perfect (I know that these platforms have brought value to people, and I also know money is tight for a lot of people); but I don't see the big services going away entirely either.
I don't think your wrong, the add-supported model is the thing most threatened by the rise of AI content, however the knock-on effects to that are concerning. Large swathes of the modern web are built on that revenue stream and while those of us who still remember (or I suppose discovered) the older web 1.0 and federated models will be fine, there's some serious concern over both economic and social impact. If all the "real" information is behind paywalls and all the AI generated junk is all anyone can get for free (which will get worse as LLMs will more and more only have each other to scrape) you're going to end up with a more severe "death of truth" than was created in the last decade through the misinformation campaigns of political actors around the world.