Easy. Tell them you have a sure idea for the next FB/google/iThing.<p>Ask them to develop the MVP and app for free as they're bound to become a multi billionaire.<p>No paperwork of course, you're friends.
"Java/Python/etc is too slow."
Then don't use it when speed is an issue!<p>"C/C++ are unsafe."
Only if you don't know how to manage memory & don't leverage tools.<p>"javascript doesn't need classes."
It's the native language of the web, it better damn well cater to the preferences of the significant propertion of programmers who HAVE to use it.<p>Generally:
"Language X is bad because reason Y."
No it isn't. You're using it wrong!
"I don't understand what this legacy system does, who uses it, why we need it or why it has to be so complicated. Can I just scrap the lot and take a day out to write something new?"