I fail to see how my interpretation of the Tenth, which I believe to be correct, would make the Constitution meaningless. If the Union were one that ensured every state's happiness, there would be no reason for any state to secede. If not and if the Union were operating to the detriment of any state or region (which it certainly was with regard to the tariff and trade), then the Tenth provides a peaceful way for states to withdraw.
Basically, the Tenth provides a check against a despotic central government, a check that I hope you would view favorably.
It would be meaningless because the Union could be unraveled by any unpopular decision the government might make. It would once again place the government under the constraints of unanimity which was the reason the Articles became useless and the Constitutional Convention was called. Thus it is contradictory to the whole idea behind the CC and the Constitution resulting therefore. Since restricting state power was the driving force behind the CC it would be absurd to place an amendment within the Constitution resurrecting that destructive power. Our Founders were not that stupid.
It is false that the 10th has ever been a check on the fedgov it and the 9th are just too vague and could have been left out of the document entirely with little effect. Hence my conclusion that they were just sops to anti-federalist agitation.