I think that gnome has had built-in IME, but at least for a long time, it wasn't possible to use a third party system with gnome, or use gnome's with other compositors. And I'm pretty sure the situation was the same for sreen readers and on-screen keyboards. The wlroots project created their own protocols to support external applications to provide such features, since that is out of scope for a compositor like sway, but there are still missing pieces.
Fedora shipped a broken screen reader for 8 years.