Here's a practical example: you have your beautiful statically typed check code in python. But still, something doesn't work, or works but is too slow. So you write, in less than a page of code, some function to instrument bits of code you care about to collect and display some relevant info as the thing is running.

Dyn Any is precisely no use here. If it's a simple on/off thing, you can maybe hack up some macro in rust, but that's a completely different (and not very well designed) language, will require you to manually modify all the source you want to instrument, and also if you want do dynamically alter at runtime what gets instrumented based you're out of luck.

Basically, there can be a lot of value in sporadically leveraging the dynamic nature of python or similar languages, even if you use it as a poor man's statically typed language > 99% of the time.