When starting a startup, don’t care about the tech in the beginning. It doesn’t really matter. As a coder I usually get this wrong. I usually care to much about the tech and the consequences are that other, more important stuff such as product market fit and actually getting customers gets less attention. The reason? Probably because it’s more fun to code in the newest framework than to talk to a bunch of strangers. But the problem is, it doesn’t matter which framework or language you use or how much faster you make your app, if no one is there to use it.
Make your app in Rails, PHP, Python, Node or whatever makes you productive and able to release it asap. Don’t rewrite stuff, don’t refactor too much, none of that matters. Get it out there and get feedback. If users think it’s slow, make it faster. At least, then you have users to make it faster for.