If two thirds of the members of the House of Representatives and the Senate voted in favor of a terrible amendment and it was sent n to the states for ratification, the amendment would be rejected by the states.
If a equally bad amendment was proposed at Article V Convention, It would need the approval of three-fourths of the states.
The idea that only Congress and not the states should be trusted to propose amendments suggests that the Federal Government is more trustworthy than the people living in the states.
If a Convention to propose amendments was held, and not a single amendment was proposed at least their would be public discussion on possible changes to the Constitution.
The Constitution is being amended every time Congress passes unconstitutional legislation. Every time the President issues an Executive Order he amends the Constitution. Every time the Supreme Court misinterprets the Constitution, they amend the Constitution.
The only lawful way to amend the Constitution is to follow the protocol described in Article V of the Constitution for the United States.