[reikonomusha]

This is true. Usually you have to convince your own colleagues, not management. (Obviously everywhere is different though.)

Your senior software engineering colleague who is a huge "Python is the second best at everything" fan will be more of a hindrance than your boss, typically. It's not wholly invalid, but it can easily become a social/political issue rather than a technical one. If someone else is proposing a popular approach (like building a backend in Python), and you're proposing an oddball one (like using Lisp), be prepared for their solution to start off with 50 points of consensus and yours zero.

[hiptobecubic]

Given that so much of building anything new and delivering it in a timeframe that is useful is risk management, I think that's the right place to start. Especially at a company where the risks of Python are mostly known and the risks of lisp are mostly not.