Mitch McConnell and the Republicans have already packed the supreme court with conservative nominees they had no right to make by their own rules.
What Democrats are proposing to do is to re-balance the court the way the founders intended. The supreme court isn’t supposed to be a bullwark against against the will of people. It’s supposed to be a protection for the Constitution.
It’s hard to imagine a protection for the constitution that has people like Clarence Hill and Brett Kavanaugh sitting on the bench.