It's the fundamental goal of the project. I know it is a depressingly overused expression but if any open source project could be said to be "skating to where the puck was", it's GIMP. And they've made a lifetime's work of it.

As a scriptable editing platform for producing graphics, it's probably usable. But interactively, non-destructive editing is now part of the basic mindset of the graphics or photography worker. And this stuff just gets kicked further and further down the road.