With what I've learned in the last five years I've (1) written a Common Lisp compiler that interoperates with C++ and uses LLVM as the backend (github.com/cando-developers/clasp); (2) I've used it as the basis of a programming environment for designing new molecules and materials; (3) we've developed a Jupyterlab kernel and ported Jupyter widgets to Common Lisp as the graphical user interface for the programming environment.
I say "I've" and then "we've" because while I started this myself - several people have joined me and we are now turning it into products.
Common Lisp is great - no other language is as rich and expressive and fun to program in. Real macros (code that writes code!), multiple dispatch, conditions and restarts - it goes on and on. There are lots of features in Common Lisp that haven't made it into other languages.
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Oh - and then there is this: http://greenlab.di.uminho.pt/wp-content/uploads/2017/09/pape... Of all the dynamic languages (and who doesn't like dynamic languages?) Common Lisp is the most energy efficient by a long shot.