> native UIs are dead.

Not in the world of macOS and iOS at least. Here native apps still rule, as there's literally no performant alternative (the OP's complaints about Markdown are misplaced - there's been no interest in MD and SwiftUI and that's why there's no good option. But in ObjC/Swift there is).

In fact, most of the apps I am using on a day to day is native. The Electron apps I use are okay (e.g. Slack) but they absolutely fail the native Turing test.