Hopefully, Krita[1], GIMP[2], and Inkscape[3] will get a similar amount of support.
[1] https://krita.org/en/support-us/donations/
[1] https://krita.org/en/support-us/donations/
There's some good stuff on the roadmap for 3.0 and 3.2 as well: https://wiki.gimp.org/wiki/Roadmap
It's getting harder to get modern quality images out of GIMP.
Also some tools that are available in Photoshop, like the many ways to smart select, or to crisp up a selection.
I almost only use GIMP any more for cropping and scaling, anything else, even if the feature is available simply lacks in quality of result.
I used to think the curve bend effect was pretty neat, to do certain types of distortions. But it doesn't do subpixel/anti-aliasing. Then WHY is it still even in there? It's not really that useful and it uses an ancient processing technique that really leaves wanting a lot in image quality.
I haven't tried the other tools mentioned in this thread, but I'm going to give them a try, hopefully they are better.
I wouldn't say Krita is not suitable for general editing, because Photoshop is also dual purpose tool - it is an industry standard both for digital artists and general photo manipulation.
Gimp starts off as an emergency last minute replacement project for two undergrads at Berkeley that does basically the same thing as Photoshop. It wasn't ever anything like Microsoft's Paint.
My argument still stays, gimp never was and still nowhere is near the Photoshop level. Krita excels both as painting and photo tool.
Old Photoshop from that era defaults to a single RGB layer. To turn it into an RGBA layer (e.g. for drawing objects with a transparent background) you need to rename the layer. Not very intuitive but Photoshop users learned to do it. In early Gimp 0.x releases how do you turn the initial single RGB layer into an RGBA layer? You rename it. This is not a coincidence.
In contrast in mspaint there are no layers, there is no RGBA mode.
Gimp is a classic old open source project in it's bad and good. It has a preset for toilet paper rolls, but it took it like a decade to support a single window mode, it has an option to rename a layer to switch to rgba mode but there is still no support for generic keyboard layouts from other software other than importing configs and resolving to third party tools (something that krita and most modern IDE routinely do)
Gimp is an emacs of photo editing that stuck in old conventions and never wants to really move forward, I could not use it a decade ago and still can't use nowadays.
For examples of 2D games with great graphics, take a look at: Mark of The Ninja, Hollow Knight, Limbo, Stardew Valley, Rayman Legends.
There a bunch of really interesting examples just using Ubisoft's UbiArt framework such as Rayman Legends, Child of Light, and Valiant Hearts.
Speaking of Ubisoft and open source, Ubisoft originally announced UbiArt as an engine/framework intended to be open sourced. It's a shame that Ubisoft never followed up on that promise.
Supposedly it hasn't been used for a game since 2015 because it was "hard to use", but that seems more of a reason to open source it, perhaps to see if community interest could help where internal-only work struggled. A lot of open source starts hard to use and takes a village to make it better. (Blender, also mentioned here, might just be a poster child of that, too.)
And yes, speaking of Ubisoft and open source - Sharpmake is a build management solution used by a lot of projects within Ubisoft and it was open sourced some time ago. Worth having a look.
I know Hollow Knight is fantastic, but it reminds my brain far too much of amateurish flash games.