She is 70 and diabetic. There is a non-negligible chance that Trump will appoint her successor if she remains.
Biden is still president, and Dems still have the Senate.
Being 70 and diabetic doesn't mean you won't live at least another 5 or 10 years. The one who should have retired was RBG. She was much older and had cancer as well as other chronic illnesses. But, she refused to retire. And, I agree it's too late at this point to replace her. I think it was Renquist who stayed on the court until he died around age 94. SCOTUS needs term limits. That would solve a lot of problems.