Remember that this whole time biden could have packed the SCOTUS and turned the Republican majority into a Democrat majority. Nothing in our Constitution says only 9 supreme court appointees. He’s just not willing to do it because he is a liberal and doesn’t want to use his power to crush the Republicans like they need to be.
If it was trump he would have (and did) wielded the knife of political power with no hesitation but the moment Democrats have the knife they hold it with fear the Republicans would accuse them of being partisan.