File picker loss of functionality is the fault of Gtk3 and Gtk4. It would still apply even in systems without GNOME at all. Maintaing a fork of Gtk3 and 4 with patches to restore 2010 era functionality would be difficult but not infeasible. Arch does some of it.

I've looked at the code and it is quite a terrible mess. It's no two line patch to change settings anymore because everything gets reset multiple times in functions you don't expect.