As a backseat lisper, I wondered, when cakelisp hit the front page, if what makes one lisp different from another really only is “the standard library”, because the syntax is so barebones, there really isn’t anything to play around with.
And then cakelisp turned out to not really be a lisp according to the author.
Semantics. CL is extremely dynamic and has separate symbol namespaces, Scheme has more rigid types, Clojure has a lot of stuff built around immutability and replaced the general use of lists with arrays, Fennel has lua types and semantics, Janet is very small and portable, and adds a lot of small nice things.
Each of these feels completely different to program in, and it's mostly not about the standard library.
And then cakelisp turned out to not really be a lisp according to the author.