They’ve been working on GIMP 3.0 for over a decade, which has non-destructive editing, as well as an upgrade to the UI toolkit (although actual UI changes are still to-do). They don’t want it to be this way, development has just been insanely slow. Mostly due to lack of developers and donations, although that has been changing recently.

They planned to have GIMP 3.0 out by May, but with so many delays it might be a few months yet.