That "What if" is a stupid idea that has been around for years. Professionals have written about this extensively - https://humantransit.org/category/microtransit for example. The fundamentals mean it can never work for anyone anywhere - including aliens with some arbitrary advanced technology.

You cannot combine fast, predictable and reasonable journey times with reasonable costs unless you have a scheduled service. If you want a chauffeured limo that is fine, don't pretend it mass transit or in any way better than a private car for anyone other than you.