I'd say krita and gimp fill different needs. Krita is for artists and Gimp is like Linux's MS paint on steroids. I frequently use Gimp to crop images, make memes, etc. When I used to draw with my wacom tablet, krita was the tool of choice.
Oh yeah, if steroids bring layers, masks, paths, a shitload of selection, transformation, and cropping tools, a whole lot of filters and loaders for all sorts of image file formats, complete color management support, 32-bit per channel processing and suchlike, then you might be correct :)
GIMP still only half-supports CMYK in 2018, though. But as someone who uses it professionally, I agree that GIMP is a Linux's Photoshop, not a Linux's MS Paint. I'm guessing that the user you replied to has only used it as such and hasn't dive into all the tools and features it offers. With all the bugs and half-broken tools it has, I still think it is a great piece of software, and my life would be much harder without it.
Photoshop had massive, productivity boosting features like Adjustment Layers, since the 4th release, in 1996!! simple non destructive effects were added to the list with 5.0 in 1998. That's 20 years ago. In 20 years, almost every single serious tool for image manipulation has understood that non destructive editing is at the core of productivity. Krita has it. Photoshop almost always had it. Lightroom has it. Affinity Photos has it. Pixelmator has it. The venerable shareware Paintshop Pro, one of the first popular Photoshop clone, grew that feature. Picasa, a free (as in beer, not as in freedom) photo library management and quick photo editing tool that was immensely popular on Windows before Google dropped it, had fast non destructive image editing.
Editing anything in GIMP feels like a painful process that allows no mistake and every single process, even just drawing a damn circle (one that doesn't have heavy artifacts by the way), takes more clicks or keyboard shortcut presses than it ever should. I know it's free software developed on some hobby developer's free time but that does not make it immune from criticism. Just because something is free doesn't make it good or worth considering. As a tool for producing content, the GIMP really is more linux's MS paint than photoshop. That's because Photoshop stopped being an overgrown paint-with-layers program since the 1996 release. I still remember how it felt to use the 5.0 release of Photoshop as if it was yesterday's. If I had no choice but to use 20 years old Photoshop vs 2018 GIMP, I'd pick the 20 years old software.
Perhaps things work better now.
See e.g. https://plus.google.com/+AmericoGobbo/posts/VK4oZv7Hobn and around.