GIMP is honestly fantastic. My workflow goes draw in GIMP, import to Inkscape to convert pieces to vector, then bring them into Godot where shaders get applied. I would rather draw in GIMP than any other program. I find drawing in Inkscape super awkward in comparison. GIMP is pretty no-frills, but it does the job. I prefer it over Photoshop. With Darktsble I've found it useful for importing high res raw images for textures too.

I don't know why people hate on it so much. It's all about using the tools you're comfortable with.