I was talking to someone a while back and they were complaining that government doesn't obey the Constitution. Of course, this person is anti-"illegal immigration" and I pointed out that this, too, goes against what the Constitution allows government to do. Surprisingly, I didn't get any pushback on this. For once.
Anyway, I said that the only thing that might have saved the Constitution would have been a clause that specified that killing politicians for any reason would never be a crime and could never be punished, and which could never be rescinded without invalidating the whole document (and thus abolishing the "Union"). This shocked her, but she didn't disagree. (I mentioned this same idea in a recent reply to a comment to another post.)
Blaming our forbears for not "defending" the Constitution well enough is just silly.
Letting government decide what's "constitutional" or not was doomed to fail-- it is always going to keep moving in the direction of more power for itself. It's always going to criminalize anything that would be effective at stopping this development.
There would have had to be a remedy that was beyond the reach of government. One that was in the hands of each and every individual; up to one person, not to the majority.
Would that have been enough? Would it have at least been better? I don't know, but it's the only thing that might have worked. The founders failed to include that, and here we are. It's too late now.