This is not about a new document. Every amendment we have has been obeyed for over 100 years, so we know they work. Former are still free, women still vote, presidents still serve only 2 elected terms.
Amendments do three things. 1) Clarify something already in the Constitution. 2) reverse a Supreme Court ruling, or 3) Add a new rule to the Constitution. Amendments are necessary to change the powers of our government from time to time and protect the will and liberty of the people or when we need to remove a power because the federal government has abused it.
By clarifying the original intent of the founders using clear concise language we can return the federal government to the limits granted in the Constitution, removing all of their own interpretations of the power they have and prevent future interpreations.