We need a Constitutional Convention because the powers of executive orders, regulatory agencies and courts ruling based on what they want the law to be are no longer being held in check by Congress or by the states. Everyone complains that Congress does nothing, but it seems to me that most things are getting done around Congress. The rule of law is supposed to be predictable, but the flow of court rulings and regulations during Mr. Obama's two terms have been completely unpredictable. The law and the Constitution mean whatever the executive branch thinks is convenient at the moment. Legislative processes have been short circuited because they are slow and messy. The interstate commerce clause has been stretched past the breaking point.
The Constitution as originally designed had processes that were supposed to balance power so that no one branch could dominate the others. It was also designed so that the states were a check on a limited federal government. The balance is gone.
The fact that who is president makes such a big difference in how the Constitution works should tell you that the Constitution is broken. A self-funding regulatory agency that has executive, legislative and judicial functions is an unchecked tyranny waiting to happen. There is no separation of powers, no power of the purse and no consent of the governed in such an entity. There should be no way such a structure is Constitutional. The fact that the Obama Administration created several tells you all how much the Administration respects the Constitution.
The structure of the federal government today has only one person that's accountable for anything and everything, the president. The Supreme Court and the appellate courts vote on party lines, but nobody can remove them, so they aren't accountable. Regulatory agencies can ignore the law, but Congress can't stop them, and under the Chevron doctrine the courts defer to their expertise. We've gone from republic to elected dictator.