...and just as a follow-up, once you've dug into the problem enough to discover it's surprisingly difficult to define what is "the right thing" for a tree-shaker in Lisp to do, you realize that even if you build it, it doesn't buy you much. That's why we tend to sound curmudgeonly about the issue. It's a valuable learning exercise, so feel free to dig in. You'll gain some valuable insights into what makes Lisp special.