I started with SML in the 1980's, implementing a core math algorithm (Grobner bases) used in my K&R C computer algebra system Macaulay. Then I got this idea there should be a related algorithm in a different problem domain (Hilbert bases) and I managed to convert my code in twenty minutes. It ran. This completely blew my mind, on par with switching from punched card Fortran to an APL terminal in the 1970's.
Everyone talks a good line about more powerful, expressive programming languages till they need to put in the work. Ten years effort to program like ten people the rest of your life? I'm 69 now, I can see how such an investment pays off.
I moved to OCaml. Studying their library source code is the best intro ever to functional programming, but I felt your "all the way" pull and switched to Haskell. (Monads make explicit what a C program is doing anyway. Explicit means the compiler can better help. What it comes down to is making programming feel like thinking about algebra. This is only an advantage if one is receptive to the experience.)
I'm about to commit to Lean 4 as "going all the way". Early in AI pair programming, I tested a dozen languages including these with a challenging parallel test project, and concluded that AI couldn't handle Lean 4. It keeps trying to write proofs, despite Lean's excellence as a general purpose programming language, better than Haskell. That would be like asking for help with Ruby, and AI assuming you want to write a web server.
I now pay $200 a month for Anthropic Max access to Claude Code Opus 4 (regularly hitting limits) having committed to Swift (C meets Ruby, again not just for macOS apps, same category error) so I could have first class access to macOS graphics for my 3-manifold topology research. Alas, you can only build so high a building with stone, I need the abstraction leverage of best-in-category functional languages.
It turns out that Opus 4 can program in Lean 4, which I find more beautiful than any of the dozens of languages I've tried over a lifetime. Even Scheme with parentheses removal done right, and with far more powerful abstractions.