Because it runs in High Sierra , why not giving the possibility to change to light mode even in High Sierra?
It would be great, and I think a lot more people will be happy to get the Pixelmator Pro because of that.
Mojave kills a lot of apps that do not work anymore with the latest system.
What features would you like to see in Pixelmator Pro?
The reason we couldn't add a light mode in High Sierra is that, for Mojave, we refreshed the overall design of the app to make it more system-like — so Pixelmator Pro on High Sierra has a very custom interface, while in Mojave, it has a practically completely native dark and light design. In order to create a light appearance in High Sierra, we'd have to create a third different interface, which would need to be designed from scratch (because the light and dark appearances in Mojave use mostly system elements, they're much easier to design and maintain). While creating a light appearance in High Sierra is not impossible, it would take as much time as creating any other major new feature and would become outdated pretty quickly, so it just didn't seem that worthwhile. And for what it's worth, from personal experience, Mojave was a very stable macOS update pretty much right from the start.