Which CL "interactive development" feature can't you get with either a jupyter notebook or ipython + autoreload enables? With a smart editor like VSCode or Spyder you also get visual variable inspections, history of executed code in one way or another etc. Only that can't easily save an "image" auto-magically, but data science and ML people wouldn't want to do this other than explicitly (eg. using fast loading formats like feather to reload semi-processed vars etc.).

I don't think you are aware how much the Python workflows of AI / ML / datasci people resemble you "common lisp ideal" ...but with a different language and better libraries :)

And if Julia succeeded, it will also bring decent performance to such workflows.

Sure, the way backend devs or devops people use Python is very static and different, but any experienced ML practitioners are at home with "interactive development".

This set of jupyter + autoreloads + editor features might get you close, but you won't be on par to CL's level. I'm thinking about CL's interactive debugger, and about language features that were thought with interactivity in mind. On an error, you get the interactive debugger, you can explore the stack frames and get to the erroneous function, change it, recompile it, come back to the debugger and ask it to resume progress from this point, and see execution pass. You didn't have to re-run the whole operation. If we can do that in Python, I've been in my cave for too long^^ As such, this is how debugging a complex program looks like in Python vs in CL: https://lisp-journey.gitlab.io/images/debugging-python-VS-li... (Ravenpack [1] is a company that does big data analysis and that uses CL, they gave some talks, maybe you'll find more practical reasons from them)

for the second point: https://mikelevins.github.io/posts/2020-12-18-repl-driven/

There might be more CL libraries than you think: https://github.com/CodyReichert/awesome-cl but I'm not that a zealot to say you can ignore Python's ecosystem, especially in certain areas…

[1]: https://www.ravenpack.com/