Why can the Power of the Court be Questioned in a Positive Way?

-It's word is FINAL -The Court chooses from 8000 Cases a Year. There is lots of Power on what it can hear or not -Can Overrule the Elected Branches of Governments and States -Also essentially Decided who was to be the 2000 President -Supreme Court acts with little Accountability as Judges are there for Life and Impeachment is bound to Never Happen -Created New Rights not Explicit in the USCON like Abortion and Same-Sex Marriage