I don't know if I'm missing your point, you're overly nostalgic, or you just never had to write a substantial X Window app back when most of these apps were developed, but nothing about that development environment was easy.
It was full of incredibly verbose, buggy API calls with a bunch of platform-specific bugs and everything was manual.
In the fine arts we call it a plastic medium. A medium that's easy to edit. It's why we sculpt out of clay instead of beercans.