The problem with appealing to "the people" is that they don't all agree what's good or bad, and indeed will give different answers to what is substantively the

The problem with appealing to "the people" is that they don't all agree what's good or bad, and indeed will give different answers to what is substantively the same question depending on how it's framed or what mechanism is being used to measure their preferences. You also need some rules to temper tyrannical majorities unless "51% of the vote means you get to oppress the minority" is your idea of a good time. And a lot of these are in the nature of a Ulysses pact. When nobody wants anybody to censor them, and everybody knows that they won't always be in the majority, we can form a general consensus that we all agree not to censor the opposition when we're in the majority and in exchange they can't censor anyone when they're in the majority. For that to work you need an effective mechanism to constrain the majority or some fool is going to steer the ship into the rocks as soon as they hear the Siren song. Then the broad consensus gets written into the constitution which in turn requires broad consensus to change. If nobody's playing dirty. Whereas if everybody's playing dirty then pretty clearly the checks and balances aren't working and we need some better ones.