IMO a bigger nail in the coffin of native interfaces was Microsoft writing a new widget library that was supposed to be better than the previous over and over again, but to this day never quite making any of them official.

Instead, I've had people from Microsoft itself recommending me to "just write it in HTML, there's no standard" and "accessibility sucks with native".

When you have the market leader telling you to write HTML for their OS, it's a carte blanche to do it everywhere.

A nail, from what I hear about that side of things, but on the Apple side I could substitute the dual replacement of UIKit and AppKit with SwiftUI that somehow still isn't good, plus separate pressure coming from all the cross-platform options between iOS and Android.

At this point, I think HTML+JS is able to be a better choice than SwiftUI for most things: Yes, some stuff will still need to go to a native layer, but that's true for HTML as well. ;P