This is like asking "why not use Haskell?" in a Kotlin thread.
For context, I've been thinking about learning Clojure.
I'm pretty new to the Lisp world--I went through most of SICP in Scheme years ago, but that's about it.
In 2012 Clojure was HN's second favorite programming language: https://i.imgur.com/toGKy21.jpg
What's the best argument for me learning a Lisp besides Clojure?
Serious question, I'm not particularly attached to Clojure, and I want to know what I will miss out on by going with it instead of some other Lisp.
I think you should try both. Lisp as a language gives you a lot more freedom than Clojure, but Clojure has a more consistent and elegant language design. Clojure focuses on mostly-pure functional programming with immutable data structures, while Lisp lets you do pretty much anything anywhere, including hacking deep into the runtime itself (Clojure lets you do this to some extent too, but not as much as Lisp).
Some videos that are worth viewing, which together I think provide a good sense of how the languages differ:
- "Common Lisp for the Curious Clojurian" by Alan Diepert. A very lucid side-by-side comparison of Clojure and Common Lisp; assumes some but doesn't really require much knowledge of Clojure. https://www.youtube.com/watch?v=44Q9ew9JH_U
- "Maybe Not" by Rich Hickey. An unusual but thoughtful take on "types" in programming, which I think cuts to the heart of what Clojure is all about. https://www.youtube.com/watch?v=YR5WdGrpoug
- "Immutable Conversations - Common Lisp" interview with Alejandro Serrano and Michał "phoe" Herda. Demonstrates the deep programmability and flexibility of the Common Lisp runtime, including its unique "condition system". https://www.youtube.com/watch?v=pkqQq2Hwt5o
You'll miss out on some of the details of cons cells, symbols and macros and such, but you'll get the meat of learning to work with a REPL, macros and all that.