Well, to return to the actual topic post, why do think adding Justices to the Supreme Court is suddenly a bad thing?
It isn't unconstitutional, no where in the Constitution does it say the Court has to have nine Justices, and the only reference to it was FDR's thought of so called packing the Court which is always portrayed as a negative
But in reality the only thing that kept the Court at nine Justices was tradition, a precedent dependent upon closure/filibuster as its' common denominator, Mitch blew that when he made approving a Justice simply a majority vote, the last three Trump Justices were approved without minority say, they are political, as would be adding additional Justices, you can think Mitch for that one
And Biden's thought is legitimate, form a watchdog Committee to determine down the road if the Court becomes strictly a partisan political entity, and if it does, add Justices to balance it out, makes sense
At least you are honest enough to admit that you want to pack the court. If your side wins and we suddenly have 13, how many should my side put in next time we win?