For all practical purposes, the syntax of Lisp isn't just a cosmetic choice, though.

Lisp was meant to be written with M-expressions instead of S-expressions anyway.

For a brief period of time over 60 years ago, yes. :)

If you want a Lisp that basically has M-expressions, try Dylan. It even started with an S-expression syntax initially and then converted to infix.

M-expressions were never implemented and never used.

Actually, variations on M-expressions have been created many times in the Lisp world. (Look what you can do with macros!) So far, none of them has caught on. The latest attempt for Scheme is SRFI-266, which creates a very nice infix expression sublanguage. If I were working on a team, I would encourage them to use this, but I don't know if it has enough traction to become widespread.

It's a common mistake to think that the syntax of Lisps are a problem. People solving the supposed problem then discover it wasn't something that needed to be solved.

Haskell's syntax comes from ISWIM, which was motivated quite a lot by m-expressions.

Except in mathematica - which isn’t formally a lisp, but practically it’s used like one a lot of the time.

it's not just the syntax. the entire language, and even the ecosystem in general, has relatively few atoms that can be combined with a higher degree of freedom than the alternatives.

it has both upsides and downsides. the upsides mostly win for me.