What’s with All These Dialogs Saying, “SomeApp is not optimized for your Mac”?

If you’re running macOS 10.13.4 High Sierra or macOS 10.14 Mojave, you may have seen a dialog that says an app isn’t optimized for your Mac. The message differs slightly between High Sierra and Mojave, with the High Sierra version telling you the developer needs to update the app to improve compatibility whereas Mojave [...]