Why are UI people so determined to make apps as opaque and unusable as possible?

> rather than explicitly toggling between “light” or “dark”, it toggles between falling back to the system setting, and the opposite of the system setting.

Absolutely NOT.

> this unavoidably indicates that some number of users don’t even know what their system theme is—or might not even understand what “system” means in the first place!

Especially these people should NOT be given two state setting that depends on something third they do not know about. Yes, some people do not care about dark vs light setting. Let them not care.