It may be a wonderful program now, I don't know, but I do remember KDE's initial efforts on the Mac -- and they were... I originally wrote "just awful," but I'll amend that to a weaker "not very good." I haven't actually seen any desktop GUI program whose primary platform is Linux really take off on the Mac, with the possible exception of LibreOffice. We have so many good cheap-to-free alternatives.
In fact I used "webkit" before it was webkit and before it was cool: I used Konqueror as my main browser (I didn't care for it being not compatible with many sites at the time, as I cared mostly for simpler, text-based sites which worked fine).
I remember all the "KDE Office" apps, various drawing programs, etc. They were and many are on a perennial semi-finished state, in a way that Windows and OS X equivalent are not. Krita has done well on that front, and a couple of others, but it took many years of not great releases. And in Windows/OS X they are non-starters as ports...
Creative Suite stuff, which actual pro creatives use, on the other hand, has been 50-50 Mac/PC sales, even though the Mac has 10% or less of the desktop market.
That's how many creatives are on the platform.
If Krita can't tap into them, it's not the platform that's at fault...
Affinity, for example, does fine, as does Pixelmator...