It hasn't made any inroads on the desktop though... all anyone did was just package their own SWA into a self-contained browser that serves its own content. They continue to be websites, with all the pitfalls of them.

I don't need to spend 2GB-4GB of RAM just to have a over-glorified IRC clone!

Also, the native toolkits are fine. Windows has two toolkits, the ShellUI/MFC family (which does everything required, although it doesn't always get hidpi on legacy apps correct; it gets integration for blind people and also unicode/multilingual correct, and also works with touch interfaces), and WinUI does it more modernly (and ticks all the boxes). OSX has its toolkit, seems to nail everything correctly. Linux has Qt (lets ignore GTK for now, only reason you use GTK is if you want to appear Gnome-native), and Qt also does native++ uplifting on other toolkits (ie, native widget + additional feature expansion, plus perfect mimicry of native look for entirely new widgets), plus Qt does everything you need to do correctly and easily.

There are also new UI toolkits coming up through the ranks that are trying to knock Qt off that #1 position. None of the WebUIs would even place in this race.

Web UI toolkits always look non-native, are hard to interpret, often use low contrast (and frankly ugly) colorschemes, are easy to use in ways that do not comply with usability standards across OSes, and usually do nothing for A11Y.

The opportunity to improve those toolkits was always there, and the ball was dropped.