It was rather uncommon at the time of its writing to have a written constitution. It's something to point to and say, "no that's not what it says, look here, it says this." I think the founders would have said nothing's perfect, there is no magic, of course the people have to decide, including by arguing a lot, whether to defend it and what detailed policy that translates into. If they don't defend it, they're f'd no matter what anyway.