Idk what the “learning curve” is. It’s not really harder to use than Photoshop for basic things IMO. If you want fancy AI tools Photoshop is better but GIMP does have some.
I use it casually.
There is some simple task I always try to do, which trips me up every time, and I always forget what it is or how to do it by the next time I go to use it.
Paint.NET is the only Windows-only software I really miss. The closest replacement I've found is Pinta, but the interface is a lot clunkier and it hangs/breaks often.