The Godot IDE itself is a "game" as in it is entirely built using Godot APIs. Makes me wonder if it would actually be a good environment to build portable business apps, sort of like a modern Visual Basic.
A native English speaker with normal vision might naively assume that they could reimplement a widget that's just as good as the native one in less than a week, but the result will be awful for anyone who doesn't match that description.
If you're building with web tech accessibility and localization are easier to add to a custom widget (though they do still require thought), but this is Godot, not Electron.
Qt: https://doc.qt.io/qt-6/accessible.html
Web: https://developer.mozilla.org/en-US/docs/Web/Accessibility
Even immediate mode toolkits can do it: https://news.ycombinator.com/item?id=33859697
Accessibility is not a reason to use first party widgets. It's a reason to use widgets with good accessibility support.