This is subjective, i do not find it better. "Period."
> doesn't let the misconceptions bite you
There are no misconceptions. I create a blank image, paint an arrow in there, want to save it as a PNG file so others can see it. GIMP complains when i try to exit because i didn't save the image. But i did, i just didn't use GIMP's proprietary file format that GIMP developers want to push.
> What you're describing is just a minor annoyance
Yes it is, i still use GIMP after all despite it. I am merely describing why i see it as an annoyance. Something being a minor annoyance doesn't mean it doesn't exist at all, after all.
Basically, you're angry because GIMP doesn't optimize its UI for MS Paint use-cases. Trading "slightly better for basic usage" with "significantly worse for any other usage" is a bad idea for a software aspiring to be a professional utility.
This is completely misrepresenting and misunderstanding what this file format even is. You might as well complain that saved games are not compatible between Age of Empires and Pokemon.
If existing formats don't support the complexity that software like GIMP requires to save a given state, then it has to fall back to a custom format. The only alternative that comes to mind is using .psd, which clearly wouldn't solve your problem since it is actually a proprietary format.
As for this "agenda" to push some proprietary format, this excerpt from Wikipedia might clear things up:
"A collaborative effort between the developers of GIMP and Krita is underway to design a raster file format called OpenRaster, modelled on the OpenDocument format, for use in both applications in a future version."[1]
To be honest, I wish some other apps that have to deal with multiple formats worked this way too.