Elena Kagen is NOT qualified to be on the US Supreme Court because she does not believe in the Constitution as it was originally understood at the time of its adoption. She would be an activist judge who ignores the clear meaning of the text of the US Constitution and instead enacts a so-called "progressive" (in reality, regressive) agenda.
In particular, Elena Kagan opposes a government of limited powers, and instead believes in a government of unlimited powers. Instead of serving as a check on the federal government's usurpation of our rights, she would be a rubber stamp supporting every statist policy that Congress and the President enact. Want to sue the federal government to stop them from requiring you to buy health insurance? With an Elena Kagan on the court, good luck, because she is going to automatically vote to affirm the law, regardless of the fact that the law violates the US Constitution.