I feel the same way although I feel that I have improved somewhat by writing an interpreter for my own programming language. The problem is we have no way to practice. I learn by writing code. If I didn't write a sorting algorithm myself then I don't know it. But how often do you find a legitimate reason to write a sort from scratch on a real project.

I think it would be great to build an entire computer science curriculum out of nothing but programming practice problems covering everything from bit twiddling to monads.