"Should I care which tech stack we use?"

I'll care a lot more than you need to.

I know certain technologies better. I'm faster and more reliable with them. At the end of the day, the best stack is the one that gets you from zero to one the most efficiently.

From Zero to One, Stack Doesn't Matter

PHP, JavaScript, Python, Go. If nobody is using your product yet, they all have the same impact on your business, which is none.

Tech becomes a real factor later, when your product actually has users and volume. By that point, hopefully you're making money and can afford a bigger team that can worry about scaling.

Tools Are Better Than Ever

With the tools we have today, you can go very far on almost any mainstream stack.

So yes, the stack matters, but not nearly as much as getting to a real product with real users.