Confused

GNOME shell will never run applets. So technically it'll be different. You could probably do the same within an extension, but nobody within GNOME is focused on providing such an experience. We want to provide the ability to make this possible though.

So there is a reason for keeping panel+applets.

But I think we both agree. Seems logical to 'remove' fallback and extensions + gnome-tweak-tool/dconf is good for people who want more control. Problem is not so much with giving control, but should be clear it is a tweak. Once it is clear that we consider it a tweak, it avoids giving the impression that it is guaranteed always work. A tweak might of course break sometimes, eventhough there is no intention to have bugs in them.

Cannot think of a good example, but maybe networkmanager/pulseaudio. We rely on it, if you do not you're on your own (sort of, this is not the best example).

Note: remove fallback in practice that it just means it is still available, but not taken into account during development. So could become more buggy (e.g. on screen keyboard might only work in gnome-shell, not in gnome-panel). Not sure though how quickly it'll become buggy or unusable. I know that system settings sometimes does things differently (hacks) to ensure it works in both.