[evdubs]

Assuming your comment applies to Common Lisp as well, if Scheme (and Lisp) truly was, "hard to read, unfit for most purposes and that even proficient coders never seem to fully grasp," it wouldn't be the language that introduced so many features later implemented in other languages.

> Lisp pioneered many ideas in computer science, including tree data structures, automatic storage management, dynamic typing, conditionals, higher-order functions, recursion, the self-hosting compiler, and the read–eval–print loop.

So many proficient coders were able to grasp features of Lisp, find the fitness of those features, and implement them in their own languages.