I'm not so sure about that. The original Constitutional Convention was not supposed to completely rewrite the Articles of Confederation either, but it did anyway.
There is no guarantee that the same thng won't happen in another ConCon. Once a ConCon is called, it can do whatever it wants as long as the states ratify its decisions. Once a ConCon is called there is nothing in the Constitution that says Congress can limit or stop a ConCon's actions. In fact a ConCon could in theory even abolish Congress. Once convoked the only ones who can stop a runaway ConCon are the states who refuse to ratify its decisions.
“I’m not so sure about that. The original Constitutional Convention was not supposed to completely rewrite the Articles of Confederation either, but it did anyway.”
That is true, but the convention still had to submit their plan to the Continental Congress. And then the Congress submitted the plan to the states, who each had a convention to approve or dispprove. I still comes down to the state legislatures to approve any and all changes.