> I mainly work in my company's monolithic codebase with about 800k lines of code, and compilation with even a simple change can sometimes take a full minute. A full re-compilation including dependencies is like 20 minutes. It's a bit much.

Agreed. My focus on Elixir v1.15 (rc to be released this week) was to improve the compilation time and I have seen increases of up to 30% in compile and boot times. It requires Erlang/OTP 26 as well. Once you upgrade, I would love to hear if it did change anything for you.