My business is working with non-technical startup founders and helping them get the technical side of the business off the ground. Your question is one I (and my clients) ask myself all the time (I'll leave out my preferred stack since it's not relevant to the question). Here are some questions you need to ask yourself:
* Are you planning to grow the business if the app succeeds? If so, how hard will it be to find developers familiar with the stack you've chosen? Or how difficult will it be to train someone to learn it?
* What is the ecosystem like? Is it already large and active? Or is it large and languishing? Is it easy to find help on StackOverflow / Google if you run into an issue? How easy is it to configure it to run on a bare VPS / EC2 instance?
* How familiar are you with the stack personally, and what's your planned completion date? If you want to get something up and running fast, unfamiliarity will lengthen your timeline. If you don't care so much about spending extra time learning a new skill, then use whatever stack you are most excited about learning.
Ultimately--and I know this probably sounds unhelpful--this is really a "feel" thing. Use whatever you feel the most comfortable with, whether that comfort is existing knowledge of the language, or the comfort is knowing that you'll be able to find help when you need it. Different things matter to different people, so I can't quite tell you what to decide, but this has always worked out for my technical decisions. Passion for your project can always overcome a sloppy or bad technical decision.