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The syntax is actually a big pro for a lot of people. I love its streamlined look that basically reads like Python once you let your IDE indent properly and learn to see "through" the parentheses (CL, Scheme).
The original language where everything is an expression and it shows. Where Python still needs an ugly ternary and made match a statement, Lisp has had the perfect IF and COND since the dawn of time.
Symbols are still a cool and useful concept that almost no other language I know of got.
The numerical tower - despite some holes - is amazing. Built-in rationals and "correct math" as sane default (i.e. 1/2 not returning 0) never get old.
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And if you let me rave about CL specifically (e.g. DECLARATIONs as "#pragma done well", restarts, CLOS/MOP, runtime READ/COMPILE, etc...), there are a lot of cool features barely copied anywhere that'd improve other languages, but these aren't part of "what make Lisp Lisp".