There may be a point to this...
Taking TurboTax as an example. Lets say I use it to fill out my tax return - it's entirely conceivable that I could create an app that does that one task perfectly adequately. If you believe the hype, I could create such a thing by vibe-coding it in a weekend. Thus, TurboTax has no utility for all those customers who just use it to fill out their tax returns (it still has value to those who maybe do other tax related things with it though).
The problem of course is that any old fool can use AI to make something that *looks* like it's filling in your tax return correctly. However, a couple of years down the line, the tax collector comes-a-knocking because you didn't do something you should have done. By then of course, everyone's forgotten any of the original story, Intuit has gone out of business and now you have no where else to go, but back to the AI.
In the short term (ie. next 5+ years), I can't see how paying for the AI credits to write your software is any better than paying for the software that's already available. At least in the latter case you know it works - and you have someone to call if there's a problem.
However, as you say, a lot of companies have made a living out of selling absolute shit which has features no one asked for, and "no one" uses, and the core features are buggy and annoying - and they're priced high because of all the features you don't use. The value of those companies is likely to fall as people realise they don't really need to suffer all the crap just to get the one gem they use all the time. AI might be an amplifier of that trend, but it's by no means the only force making it happen.
FWIW, I foresee a load of new SaaS products coming along (quite probably AI-created, or at least rapidly developed). They won't be super complex or all that clever, but they'll be cheap and easy to use. They'll do what they do excellently well, but they won't do a bajillion other things most people don't need. Since they're small, they'll be cheap to manage, cheap to run and so really will cost less than the (AI credits + hassle factor) to build it yourself.