> I know why QT/GTK and various other GUI systems use a HTML-y grid layout, but for me personally, I always struggle to make nice looking, well laid out, functional GUIs with them.

There's a very intuitive drag-drop GUI designer for GTK+, namely Glade. Sadly, it was abandoned as GTK+ transitioned to 3.x and 4.x. So the only supported workflow now is laying out your GUI in code.

The intuitive "action-oriented" language should not be underestimated either. Though I assume it could be made idiomatic even in modern languages, by leveraging their support for the async programming model.