"ooh, so it's primarily a Linux program"
- No. It is intended to be Cross Platform, just, to put it bluntly, Windows is much shittier to work with, and it's much harder to make things work correctly on Windows than on Linux. Krita is built on the Qt framework (Used by Nokia, NASA, Tesla cars and others) which is Cross Platform.
As development gues on Krita is constantly compiled for and tested on both Linux, Windows and Mac. The Linux version usually works pretty well, and issues are easy to fix, while the Windows version tends to be half broken and requires lots of fixing, and the Mac version being broken badly. D
They constantly work on fixing everything on all three paltforms. Some time ago Krita was completely useless and broken on Windows, and Mac version didn't even exist as such, so it's a big improvement already that there is a more or less working Windows version and the Mac version is already being tested by some people.
One thing that makes development of the other platforms harder is that the vast majority of the developers and users - as well as the Open Source community in general - are Linux users, so there are few people able to test it on Windows, and even fewer on Mac - and most of those people never take the effort to actually submit feedback.
If you want Krita work well on Windows, keep testing Windows builds then go and submit bug reports, and follow up when devs ask your help in testing. It's up to us users to help Krita getting better.