the thing about gimp and krita is: gimp is an image manipulation software and krita is a drawing software, and as far as i can see from my so’s work, photoshop is a somewhat mixture of those two. from the jump, we’re not comparing apples to apples, unfortunately.
but you already answered your own question, i think.
see, foss programs aren’t there to be a drop-in replacment for their closed sourced alternatives. they emerge from a need from the community. what is more, usually you will have multiple programs encompassing a single workflow of their closed sourced counterparts; meaning they are modular.
so even if there was some other program apart from these, it would have a learning curve, unless adobe open sources photoshop. so there is a viable alternative (which i know from experience) but there is a learning curve, albeit a steep one for someone coming from photoshop.
you shouldn’t limit yourself, but it would immensely improve your understanding of the software if you try to recreate simple pieces of your workflow using gimp, once in a while.