It can be trivially changed in the sense that it's a computer program that simulates money. No amount of consensus can increase the gold supply.
There still has to be consensus on using gold as money, if there isn't it will lose its monetary premium to something that has better monetary properties.
This is a great point. The choice to value gold as currency over other rare metals is 'a cultural property of the community' and yet not 'trivial' to change, just as Bitcoin's consensus isn't.