Lisp is only a general idea about syntax and macros. If you want numerical computations you want a big library like blas, and the problem is about efficient memory allocation, cache and garbage collection. If you want deep learning you want a big library.
Lisp is like arithmetic, without more concepts or libraries it doesn't work, you have to reinvent the wheel.
R provides near 8000 useful packages, that's what makes a language a useful tool to solve a problem, and it can call routines in C, fortran or use C with armadillo. To sum up, a language without a great community and specific libraries is not a way to fix the world, on top of that there are few jobs using Lisp. Clojure is trying to take advantage of all those java libraries, that is a good step in the right direction. Clasp is another idea trying to use C++.