I don't think it's nearly as easy as it sounds in your head. Minecraft's existing player base is Minecraft. Not just blocks you can dig and build stuff with.
https://www.quora.com/How-many-people-play-Minecraft
It's staggering. And it has a life of its own. You get one of the best modding communities out there because of the popularity. This is not something someone can just make a clone, even a great one, and the community would just jump over. It would just necessarily divide the player base, thus the modding interest.
This is what we're stuck with for a good long while. I think it would take Microsoft literally killing off the Java version to ever prompt any major change like that, and I don't think even Microsoft is that dumb.