Tcl/Tk is pretty good in terms of rapid development. Unfortunately it has stagnated quite a lot over the years.
Gtk on the other hand is absolutely terrible and its developers don't help by completely rewriting things every few years and breaking all existing code in the process.
Have you tried WinForms? It isn’t the latest hotness so Microsoft has to be dragged kicking and screaming to support it in current VS, but they were forced to do so because corporate developers still have some clout.
I still think that WPF was the peak desktop UI framework. Extremely powerful with lots of small composable primitives, can easily do declarative but drop into more traditional event-driven imperative style where it makes sense.