I agree that the lack of standardization around the "insecure" things is a bad idea. Insecure operations don't have to be available by default, or even universally supported, but a central registry of interfaces for e.g. retrieving all windows on a desktop would certainly help preventing fragmentation.

At the same time, most of this post really is just a rant essentially saying that a low-level library is so flexible that using it directly results in code so verbose it can hardly be read. Yes, that's how good low-level designs always are.

You can turn a generic portable asynchronous ANSI C interface into a simple, blocking and platform-specific one with an abstraction layer. You can integrate it with all sorts of existing event loops and programming frameworks. You can customize it all you like but using it directly in an application will cost you a lot of patience. At the same time, you can't go in the opposite direction; from a "simple" blocking black-box interface to something that can reasonably host a complex GUI toolkit. If you're after simplicity, go higher-level.