> eg: do most people really understand the geometry or science to prove the earth is round?

During the "there are flat-earthers" fad I realized that for the majority of people it doesn't matter whether it's flat or not, the question whether it's flat or round actually only arises when they need to perform an action which depends on the Earth's shape, which is never, because most people are not pilots, not astronauts, etc., so for them, the model of Earth being flat works perfectly well.

It's the same as people saying that Earth is round for most intents and purposes, and then a smart-ass saying "actually, it's not a perfectly round ball". Yes, it's not a perfectly round ball, but we're discussing time zones here, not local weather patterns.

Most people say that Earth is round not because they believe it's the correct model for their use case, but because they want to belong to the club of people perceived as smart, and that's the view expected of a "smart" person. The flat-earthers perfectly uncovered this charade, by showing that most people just parrot "Earth is round" because that's the social consensus which just so happens to be true.