I have to admit, I am a bit saddened to see reddit give up on Lisp.
“If Lisp is so great, why did we stop using it? One of the biggest issues was the lack of widely used and tested libraries. Sure, there is a CL library for basically any task, but there is rarely more than one, and often the libraries are not widely used or well documented. Since we’re building a site largely by standing on the shoulders of others, this made things a little tougher. There just aren’t as many shoulders on which to stand.”
However, having struggled with trying to find good Lisp libraries for building a web app, I can fully agree that most of it has to be built from the ground up. This adds much lead time. Even if it is quicker for a good coder to write a library in Lisp, you still have to write the library and not the application. I am somewhat surprised they chose Python over Ruby, but for ease of translation, I can see some of the benefits.