I'm curious because I thought the main draw of CL was that it was easy as heck to roll your own library support.

It's easy to roll anything in CL if you know what you're doing, but making it talk wsgi or generate pngs isn't trivial, no matter what language you're writing it in.

CL implementations do have an FFI that you could at least call C libraries from, don't they?

I think so? I honestly don't know, I never really worked with the CL codebase, I just used it for reference sometimes. But even if it did, I'm not sure how much velocity is gained by using CL vs. Python, especially when making a web app, where there are so many examples, libraries, and frameworks out there to help in Python.

While I have admittedly limited experience with it, CFFI worked awesome for the couple things I tried to do with it. I don't have any CL code in production yet, but enjoy using it when I'm doing some recreational programming, or looking for something that's easy to embed in a C program (Lua's nice, but it's trivial to take the ECL Common Lisp implementation and hook up emacs-slime to it, even when it's embedded in a C program)

Lisp shines for codegen and creating DSLs and new control structures, but if you're just writing out tedious imperative code, it isn't really better than Python. Its lack of popularity means it can't offer as many libraries waiting to be reused.