The key to this idea is the voting system. Because the voting system ensures (against fake accounts & bribery) that everyone has a fair vote for what goes into the game.
So we'll have to assume a perfect voting system is possible. ( I can get into this in detail if you want me to; but else where. The underlying tech is amazing.*)
The only challenge remaining is if a opensource team (potentially hundreds of devs) can handle the influx of different ideas. They will be incentivized too. And don't worry, it's not a "pay for more votes" gimmick.
All systems for magic, generated structures, NPCs', missions, lore & more need to be interwoven. Just as all the diverse mechanics of minecraft are
now. All the little details like how dogs eat bones, so skeletons are afraid of dogs.
I want to get on a discord call for people with ideas.
* [ now after playing for 2 weeks straight] I actually want to demonstrate the power of this voting system with minecraft because of my first hand experience. I thought about it before, but this is the first time in a long time I played minecraft and it hit me like a truck. Minecraft makes perfect sense for this.