You can still run GIMP on Mac. I do and love it.
Krita is better for people who need to do a lot less than what the GIMP is capable of doing.
People do photo editing in Krita just like people do painting in Photoshop. Both tools can do both, as can GIMP, it's just that most of Krita's new features of the last few years have been focused on painting.
Also if what you said matched reality, Corel Painter would still exist in a meaningful way in 2020 but most artists migrated to Photoshop for their painting needs in 2007
If it's your definition of photo editing then any freeware (ie: xnview, windows' image viewer...) can do this. You don't need Photoshop - which is pro high end software - to do this kind of basic stuffs.
I'd also be surprised if they allowed to change the white balance or do color curves - especially when you look at the amount of super powerful filters come with GMIC, which itself comes with Krita. They also most certainly don't have a "Repair" tool like Krita does (https://streamable.com/p5dd1k).
GIMP is not really a good image editor, when you compare it to the alternatives and include paid alternatives in the comparison. From my memory of using Photoshop, I’d say that GIMP is roughly equivalent to Photoshop 3.0, which came out in 1994, although it is missing some core features from Photoshop 3.0 (and prior versions—the workflows that I used in Photoshop 2.5 are unworkable in GIMP, as far as I can tell, and it’s extremely frustrating to try and use GIMP for basic tasks).
I love FOSS, but I also like creative/ great products by small to mid-size indie developers like Pixelmator. For what I do, it's fantastic, they have a iPad app too which is where I do most of my photo editing.