Notarized Mac apps have to used the hardened runtime, which comes with a few restrictions. For now, there are no content restrictions for notarized apps on the Mac. Let's hope it stays that way. But there are very significant content restrictions for notarized apps on iOS, and who knows how long until Apple introduces them on macOS as well.
I haven't been an Apple user for over 10 years, through that macOS now uses the App Store to distribute OS updates. There is no getting around the App Store on macOS and must be used for Apple related software releases, such a Xcode.
The community that looks for applications not in the App Store is most likely quite low. It requires knowledge of the ability to side-load, how to do it, and where to find applications that can be side loaded. Homebrew installation ratio against total macOS users might be a good metric.
I have five apps that get regular updates via DMGs, two of which are unsigned and do not meet Apple’s sandbox requirements.
All I have to do is authorize them to install in settings.
You and I can agree on Apple’s App Store power and abuses, but you can still call MacOS a computer OS.