No it is also not an OS problem, it is a problem of perverse incentives.

AI companies have to monetize what they are doing. And eventually they will figure out that knowing everything about everyone can be pretty lucrative if you leverage it right and ignore or work towards abolishing existing laws that would restrict that malpractice.

There are thousand utopian worlds where LLMs knowing a lot about you could be actually a good thing. In none of them the maker of that AI has to have the prime goal of extracting as much money as possible to become the next monopolist.

Sure, the OS is one tiny technical layer users could leverage to retain some level of control. But to say this is the source of the problem is like being in a world filled with arsonists and pointing at minor fire code violations. Sure it would help to fix that, but the problem has its root entirely elsewhere.