I think some of you gleeful Reps are missing the point of the “illegitimate” discourse. It is of course obviously true that the reason Garland wasn’t confirmed and the reason ACB will be is that the Reps have the power. They had the political power to block Garland to the point of not even having to go on record as voting against him, and they now have to the political power to ram ACB through without a care for how obviously hypocritical it looks.
But by making the whole shebang about “raw political power” and no respect for norms or whatever, the Reps are giving the Dems a lay up for packing the court (or removing jurisdiction, or one of the other better reform suggestions that are floating around). FDR got flack from his own party because his openly political attempt to “rig” the courts was... a “norm” violation. By setting up the standard of “whatever I have the power to do I should do, norms and civility or whatever be damned,” the Republicans are openly inviting court shenanigans whenever any party controls both Congress and the White House, and simultaneously undercutting the best check on the abuse of power. If nobody care about institutional norms, then there really isn’t a good reason for each side to just pack the courts whenever they can.