This is not a great substitute for installing through an app store because the app will not update automatically.

This is, however, a great thing to have.

A better substitute would be using F-Droid. By the way, some free software apps are not gratis on the Play Store but are on F-Droid.

It can still be confusing to manage two app stores for some people, while installing an app from a downloaded executable is usual on Windows, so Krita probably did the right thing.