So, dynamic scoping are global variables... except with even way way way worse unpredictable behavior. Any function from three-level remote libraries can invisibly modify the meaning of code.

Sure, it allows for neat tricks, I suppose. It mostly allows impossible to diagnose error conditions since what happened actually depends on anything that may have happened before, invisibly.

I find it particularly amusing since fighting off global states has been a worthy goals of languages, libraries and framework. Without it, you can say goodbye to reproducible behavior and multi-threading.

(If dynamic scoping is thread-local, you still have the issue that anything can affect anything else, so nothing can be assumed to be reentrant anymore.)