I'm assuming Iced has no A11 support (these projects never do). Probably no RTL support. Possibly no reusable "system" widgets like open/save dialogs.
Anyway although a11y and i18n support have not been implemented, they are planned.
If Iced actually gets cross-platform accessibility support, that's great! Very few projects have that today. More certainly wouldn't hurt. But until it does, you shouldn't base a DE on it.
Edit: The issue you linked to is about RTL support. That's also required, but doesn't touch on a11y.