It's nice if you want to run a server on a pi
The lua plugin system is well-developed and documented  so most plugins could be changed over easily.
- WorldEdit: https://forum.cuberite.org/thread-870.html
- Essentials: https://forum.cuberite.org/thread-1840.html
But also minigames like
- SkyBlock: https://forum.cuberite.org/thread-1508.html
- HungerGames: https://forum.cuberite.org/thread-1456.html
At that point, why not just switch over to Minetest? Given enough work, it could eventually be an attractive and feature-complete clone — and be nicely extensible too.
The fact that Minecraft ran so well on so many machines enabled it's huge success. I don't think most programmers are capable of that feat.
You have to remember that Minecraft's world format, server-client architecture, and username system all underwent massive changes, all of which could have been avoided in the first place. It's also worth mentioning that Minecraft runs well (which I would contest) on modern hardware in the same way DOOM does; not asking for much in the first place doesn't absolve your work from horrid inefficiencies/long running bugs.
If he had waited and engineered a solution suitable for a billion-dollar business up-front, would it ever have shipped and become a billion-dollar business?
What makes it a good alternative is that it's reasonably lightweight. We currently have a server running on a RasPi 1 B where people can build structures for the world generator: https://forum.cuberite.org/thread-1372.html