> There's never really an explanation as to why "we have to treat these things like infallible perfect works" when they're not, and even their authors told us they're not.

They are not, though. The constitution can be changed and has been changed many times in the past. I assume they think (or justify their decisions by saying that at least) that it’s not their job to pass legislation or enact constitutional amendments without any input from the states/congress which seems like a reasonable viewpoint.