Apologies, keeping things brief on my phone often backfires.

What I meant is that most of us don't have the same content that needs to be styled differently across different devices. Majority of the time, things are easier. As you mention, use the predefined UI elements and call it a day. It is sadly hilarious how much better that would be for most applications.

For things that do have content that wants custom styling, think games and such, you are almost certainly either inventing your own abstraction language and porting that to different targets, or just creating a new implementation for each target. Yes, some folks have tried to make uber languages where you "write once, run everywhere." Those are almost always subpar compared to "write once for everywhere you care about running."

I'll say that I do agree with the argument on its merits. However, I disagree with the argument on evidence. Statistically, the style/content divide has really just increased the complexity of the code I deal with.