I never implied any of that. I said that developers don't need to rely on others to ship *their* software to end users, the developers can take control for themselves.
The developers still have to deal with the environment their software builds in and how it works for end users, but now they don't have to worry about their software running on hundreds of different systems and needing to find *very* specific bugs within each one. System bugs go to the system developers, application bugs go to application developers. System bugs don't go to the application developers.
Flatpak doesn't at all take away the need to worry about the infra; that's Flathub's job, but even then, they force developers to build offline, thus needing them to think about it.