Can you point to the law McConnell violated in doing this? And if not, in what sense is the current court illegitimate? Finally, how does this in any way address my question about the president "seizing" power?
So maybe he didn't violate the law, but he certainly didn't uphold his Constitutional responsibilities, which I believe is part of the Oath of Office he took.
This is how Congress and the co-equal branches of government are designed to work. Congress and the President often don't get along. It's a feature, not a bug.