Dumb question: Why do we need many independent Node.js runtimes?
But that points to an important aspect of the platforms-game: The interface between the runtime and everything else should be standardized, to support true pick-and-choose.
Just saying don't throw out the Common-JS sub-system with the bathwater.
The problem with ES6 modules (imo) is it does not support sync loading of dynamic imports, so you have to figure out how to handle the Promise.
This have a similar analogy with browsers. Back then when Internet Explorer was the only supported browser, the websites were not evolving as fast. When Firefox pushed it forward and then Chrome, customers won (better and faster sites).