I'd counter-argue the ideas written on it are still pretty viable. I:E. Freedom of speech, press,religion,trial,due process, and so forth...
Yeah, America was a republic, which is now what is generally seen as the best kind of rule, today. Would you want to live by the standards in the 1700s? Anyhow, I looked up the constitution, here is something else the constitution definitely was not accounting for.
"In suits at common law, where the value in controversy shall exceed twenty dollars, the right of trial by jury shall be preserved, and no fact tried by a jury, shall be otherwise re-examined in any court of the United States, than according to the rules of the common law."
20 $ in 1783 against 20 $ in 2016? They shouldn't be expected to know economy.
"Excessive bail shall not be required, nor excessive fines imposed, nor cruel and unusual punishments inflicted."
Yet the death penalty is still used (and I believe you support it, despite it being constitutionally banned).
"The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people."
Hmm, the government forces upon businesses minimum wages, affirmative action, and serving all customers they get, but this is supported by the majority of Americans.