If Biden wins and adds more Justices to the SCOTUS, that's not "Packing the Court", it's "Expanding the Court". He would have the constitutional right to do that just as much as the Republicans have the constitutional right to put someone on the court that is obviously the biggest demonstration of political hypocrisy in generations.
The objective is to have a balanced court.
FDR had to deal with the 9 "old men" that were ultra conservatives, and they made the "New Deal" difficult to implement, but when FDR ultimately overcame the obstacle of the court it lifted us out of the Great Depression just in time for WWII.
Naturally conservatives became convinced WWII was the reason for our financial recovery.
Conservatives are wrong.