I agree that that hiding important buttons behind an extra click may be a bit of a UX downgrade, but honestly, it's not that hard to find.
There are multiple ways to access it, anyway:
You can open the dropdown arrow next to the Play icon and choose "Debug layout".
Or you can press Menu > Project > Debug.
Shift+f4 launches Debug for the first layout.
Shift+f5 launches Debug for the current layout.
It kind of sounds a little like you want Scirra to redesign their interface just because you don't want to learn where the new button is?