Well the Constitution is the Law of the Land (Art VI, Sec 2, Supremacy Clause) whether you see it as a contract or not, with or without the 17th Amendment. The 17th Amendment does not overturn the Supremacy Clause.
The Constitution is the only legal bulwark of freedom against the tyranny of limited federal government power.
If the Constitution doesn’t delegate the power to the feds by a good-faith reading of the text and original understanding and intent of the ratifiers, then it is not a legitimate federal power. Most federal activity these days is unconstitutional.
The Constitution along with America, was handed over to the American People. As oft quoted, Benjamin Franklin coming out of the constitutional convention famously responded to a question, “Well, Doctor, what have we got, a republic or a monarchy?” with the response, “A republic, if you can keep it.”
This is the very heart of the issue. It is not too complex, but something we must learn, keep, and guard with “our Lives, our Fortunes and our sacred Honor.”
It’s just a point that needs more refining. I tend away from a contract because contract separates the the parties and actually creates a Federation on superior footing to the States.
As a treaty, the states and the federal government are inextricable, and the Senate was the tie point.