The constitution is a tool. The fact that American citizens have chosen to appoint public servants that refuse to use it correctly is not a reflection of the tool.
"Let it simply be asked, ‘Where is the security for property, for reputation, for life, if the sense of religious obligation desert the oaths...?"-- George Washington
Without the people using it effectively, a Constitution is "just a piece of paper." Tools don't use themselves.
That's why the failure of the people to effectively use the Constitution is metaphorically equivalent to the failure of the Constitution. Saying that "Constitutions don't work" is just a metaphor for the assertion that the subjects of a state can't/won't use Constitutions to protect their liberty. They never have, and never will. Not for any historically significant length of time.
“The man who puts all the guns and all the decision-making power into the hands of the central government and then says, ‘Limit yourself’; it is he who is truly the impractical utopian.” ~ Rothbard
“I go on this great republican principle, that the people will have virtue and intelligence to select men of virtue and wisdom. Is there no virtue among us? If there be not, we are in a wretched situation. No theoretical checks — no form of government can render us secure.” ~ James Madison
"If men are good, you don’t need government; if men are evil or ambivalent, you don’t dare have one." ~ Robert LeFevre