It’s extremely important, because you’re never really picking a programming language, you’re picking a stack

You can technically write an android app in Python, but should you? You’re now locked into a framework used to run apps in Python, which are going to be much more limiting than other languages and frameworks. But you’ll also have access to Python libraries, which gives you options in that direction

Then you examine the context. How good are you at learning other languages? How long/complicated is what I want to do? Does this need to be performant? How long do I need to keep this working?

And most importantly, and you really have to think this one through… Will I need to extend the original goals in the future?

So really, yes, it’s very important. A bad decision in the beginning could cause problems for decades