Could the web disappear due to mobile apps and AI?

I don't think so. It might get smaller and nerdier, yeah. But I'm on Mastodon, and there's a strong anti-AI and app (not in principle, I believe, but in practice; they tend to be more privacy-invasive than an equivalent website, whichh is a major part of their appeal for companies) bias. I don't think indie/small/whatever-you-want-to-call-them websites are hopping aboard the bandwagon either.

I could see the feel changing and it becoming less "oh, of course you've visited a website" thing and somewhat more of a conscious choice, but vanishing? No.

I don't think websites are going anywhere.

Mobile apps break frequently and you can't deep link to them. AI is bad and won't last.

There are a lot of mobile apps that are webviews pointing to an already public website/web app.

It disappeared already because apps now have the biggest share of users attention.