Why would everything have to cater to the lowest common denominator on the scale from computer-novice to power-user? Those can just use Windows or Mac OS, or maybe Ubuntu. But why would their use cases invalidate mine?

Also, IDK how things are on Apple computers but on Windows no two apps look similar, so the common user should not have more difficulty with diverse UI paradigms on current Unices than on Windows.

In that case you can simply use a distribution that makes the choice for you. Generally people recommend Ubuntu or Linux Mint here.