You're overstating the case, but I think there's a strong possibility people will prompt AIs to produce bespoke apps that solve their niche use-case rather than paying a developer to do it.
I pay for a SaaS app that tracks my finances, but it's not that great and missing some features I would like. Very soon I expect I'll be able to get a better, local-first replacement tailored to my needs by prompting Claude & Friends.
I think developers overestimate the amount of people who want to create app. My friends are lawyers, doctors, musicians, Pr, sales and they really dont care about creating their own apps or software. They use their iPhones for calls and Instagram.
There are two big advantages to using a 3rd party system.
1) There are a lot of cases where aggregated user data, even if anonymized, allows for insights that you can't get using just your own data.
2) The software is really just a stand in for a process. A way of doing something, like record keeping or tax filing, etc. A lot of times it makes sense to follow an already established process rather than creating your own. You are less likely to encounter unexpected pitfalls that way.
I don't see how you can overcome those just by having an AI that can build simple crud apps at will.