I (distantly) knew an indie software developer who was putting up a pretty good Photoshop alternative in 1996: ONE GUY alone in his bedroom was making a decent living selling a Photoshop alternative that he wrote himself. And he wasn’t exactly a super-wunderkind coder, just a guy who knew the photo manipulation space well enough to get enough customers to float selling his software for a few years - in direct competition with Photoshop.
Adobe isn’t selling magic dust ground from precious gemstones by thousands of artisans. They had a decent product that they marketed the hell out of and eventually got overly greedy.
GIMP, Krita, and many others are right up there if you haven’t been sucked into the Adobe addiction vortex.
Maybe I’m doing too much engineering - I found Open SCAD to be way easier than Blender for making stuff, and that’s saying something because Open SCAD is quite a pain.