If a large majority did, yes, it could be changed. And obviously a piece of parchment cannot force people to do something if people unanimously decided to do o

If a large majority did, yes, it could be changed. And obviously a piece of parchment cannot force people to do something if people unanimously decided to do otherwise. But preventing the whims of the just-barely-a-majority-of-those-who-voted from changing such an important thing, is important and useful.