In case of the Dropbox please read this:

_But as the company grew, new engineers who joined couldn’t understand the code. Clever code is usually short and cryptic, written by and for the individual who came up with it, but is hard for anyone else to understand—and nearly impossible to maintain. Guido called this “cowboy coding culture”. He recognized its value in our early stages of trying to implement things quickly, but knew it wouldn’t be sustainable over time, so he decided to speak up in his own quiet way._

And now they'll have to rewrite everything in programming languages where maintenance is not a burden.

[0] https://blog.dropbox.com/topics/company/thank-you--guido

Your last point is not supported by your link - this is an article praising Guido, the creator of Python, and remarking how good Python is.

Sorry, my bad. They already started rewriting core components in Rust.

Here you go:

https://dropbox.tech/infrastructure/rewriting-the-heart-of-o...