I think you just proved my point. I presume your project to "learn a bit more about compilers" was not commercial in nature, and yet you chose Common Lisp. Whether a project is for fun or for profit, I'd prefer to not waste my time, and it appears you feel the same.
I think the survivability (not popularity) of a programming language is closely correlated with its usefulness to programmers.
Of course, the best way to rebut my implicit assertion is to actually "put together a substantial application" with Arc instead of talking about it, right?