I still don't use Lisp for any real world projects, but it was useful for helping me better understand concepts in other languages, particularly JavaScript and Python.
Learning SmallTalk was also helpful with regard to message passing.
I think that the ideas that were brought forth in MetaMine[3] where quite interesting. The ability to mix declarative and imperative code in the same program, without melting your brain doing so, was a very powerful tool. I'm sad that it hasn't resurfaced. (I did find a fork of it on GitHub though[4])
[1] https://en.wikipedia.org/wiki/Literate_programming
[2] https://en.wikipedia.org/wiki/ColorForth
[3] http://web.archive.org/web/20201014024057/https://www.youtub...
https://www.syncfusion.com/succinctly-free-ebooks/assemblyla...