GIMP is open source if you want to go help improve it ;)

I tried ;) GIMP developers aren't very open to external contributions. I don't consider my attempts to be of low quality either, but the bike shedding resulted in them never being accepted. "It's best to wait until X lands" or "I think this will be part of Y".

Meanwhile, 10 years later, the functional features I've tried to contribute are still not possible in GIMP ;)

Yeah, I was mostly being facetious haha. I know that GIMP as a project is notoriously difficult to contribute to.

If someone actually has the ability to do instead of just complain, the answer is to fork it and welcome more patches.

https://en.wikipedia.org/wiki/GIMP#Forks_and_derivatives There might be one already, of course.

If it works well enough for the people who use it, why does it matter?

It doesn’t work well enough for the people who use it; false assumption. I use it, and it’s a cludge that I resent every time I have no other option.