I think it may be more of a question of whether our government actually follows the stated principles as might be found in official or historical documents, or if there's a disconnect between what our leaders say versus what they actually do. Do they mean what they say? When Thomas Jefferson wrote "all men are created equal," did he really mean that? It sounds good and might make people feel warm inside, but if it's not practiced in good faith on a societal level, then it just turns into an empty slogan.
Most politicians are lawyers, and the funny thing about lawyers is that they'll look for loopholes and technicalities and bog things down in procedure. They don't seem to look at the Constitution in terms of supporting the rights of the people, but more a way of looking for "what can we get away with and still be legal?" The irony of it all is that, throughout history, many rights have had to be secured because it took other lawyers to remind the government of what the Constitution actually says.
So, in other words, plagiarizing another society would do no good, not if the people entrusted with stewardship over the government and legal system are a gaggle of corrupt sleazeballs and pettifogging martinets. If a government does not follow its own stated principles as they are written on paper, then it becomes a hollow institution.
Your argument engages the question of "originalism" versus "living constitutionalism." That question expands to engulf much of the debate between the Right versus the Left. Furthermore, the question of originalism versus constitutionalism hinges on the physical laws of thermodynamics.
Originalism interprets the second law (negative entropy is never created) to imply that all the good (negative entropy) that can come out of the Constitution had to be in it in the first place, since negative entropy is never created, only guarded. On the other hand, living constitutionalism implies (in a round about way) that negative entropy can be created in, or by, "living" organisms. Living constitutionalism sees even a written text, dead letters (in Pauline terms) as living entities able to produce negative entropy rather than just storing and guarding what already exists.
Conservatism, in a general sense, wants to conserve the negative entropy that exists, while liberalism, believes living organisms can create new pools of negative entropy. If the latter is the case, then the Constitution is merely a framework manifesting the brilliance of the men who wrote it, even though, in the dead letter, it's inert and worthless without being interpreted and re-interpreted by living readers of the document. Googling the terms:
Originalism
This method interprets the Constitution based on the original intentions of the framers, as they were understood at the time of the Founding. Originalists believe that the Constitution's text has a public meaning that has not changed over time. They often oppose amendments because they believe changes to the Constitution would detract from the original intent.
Living constitutionalism
This method views the Constitution as a living document that can be used to guide the current government. Living constitutionalists support amendments and view the Constitution as a malleable expression of the will of the people.
Conservatives tend toward originalism, while liberals are more like living constitutionalists.
John