We used to get along just fine on things like Qt, Gtk (perhaps via Wx), or indeed Tk - in some ways still my favorite after all these years. But then 'easily' wasn't necessarily the gold standard of everything.

The electronisms I occasionally have to use are glorified chat-apps like Signal. Hardly complex UI cases.

By comparison, I wouldn't consider VS Code a "simple" UI. And replicating it with Qt, GTX or anything else would be a significant endeavor for even one platform, let alone three very different platforms. They all have serious flaws. As a user, I'd rather have something useful now, than wait a couple years hoping to maybe see a linux or mac release of a program.

To each his own, of course, and if VS Code does it for you, well then - excellent.

I personally find it a bloated mess, and like to stick with my Komodo and my Geany - two neat examples of portable UIs done right.

Anyway, I'm sure there are ways of embedding runtime web macinery in somewhat less than 100Mb. Twenty years ago I did so in a megabyte or two, admittedly without the js.