I can see how RT would have problems getting on the App Store… App Store Review Guidelines - Apple Developer
2.1 App Completeness … We will reject incomplete app bundles and binaries that crash or exhibit obvious technical problems.
RT is still experiencing crashing on quit on mac. https://github.com/Beep6581/RawTherapee/issues/3882#issuecomment-304544290
2.4.5 Apps distributed via the Mac App Store have some additional requirements to keep in mind:
(i) They must be appropriately sandboxed
That looks like quite an undertaking! App Sandbox | Apple Developer Documentation
(vii) They must use the Mac App Store to distribute updates; other update mechanisms are not allowed.
… So one would only be able to update via App Store.
2.5.9 Apps that alter or disable the functions of standard switches, such as the Volume Up/Down and Ring/Silent switches, or other native user interface elements or behaviors will be rejected. For example, apps should not block links out to other apps or other features that users would expect to work a certain way.
RT also has issues with certain F-key shortcuts on mac and system reserved functionality. Some keyboard shortcuts not working in macOS · Issue #3510 · Beep6581/RawTherapee · GitHub
The Mac App Store is convenient enough to keep some utilities automatically updating, but I don’t see RT fitting into Apple’s constrictive ecosystem at present. Even if RT was an idealized mac app, that the app must only be updated by the app store doesn’t make sense to me.