A quick look at what Quicklisp has to offer for libraries should quickly convince people that fooling around with anything but Common Lisp would be very energy-consuming.
A quick look at what the job market has to offer (for those who interested in Lisp) should quickly convince people that learning anything but Clojure would be not only energy-consuming but also impractical.
Knowledge and skill useful for finding a job is not all the knowledge that is good.
Clojure was developed by someone called Rich Hickey. Not only were there no Clojure jobs when he started hacking, there was no Clojure. That's a textbook example of an energy-consuming and impractical waste of time.
For almost every piece of technology listed in a job ad that you think is worth knowing, someone had to put in a whole lot of time and energy, not knowing if it will pan out at all, and often that time and energy were uncompensated by anything other than the existence of the thing in the end.
It's also an actively developed modern language not stuck in the 80s.