We could imagine some new way of operating over systems: for instance the Alan Kay original meaning of object-orientedness [2], or instead of a compiled binary to have some stable diffusion model + large language model which hallucinates the OS on the go [3].
But that's not what the quantifiably greediest person on the planet has in mind, by "everything app" they just mean "everything must be controlled by me, not by you".
[1] https://en.wikipedia.org/wiki/History_of_operating_systems
[2] https://www.youtube.com/watch?v=QjJaFG63Hlo
[3] https://arstechnica.com/information-technology/2022/12/opena...