Next time you want to argue the Constitution do so with Scalia....his words about what originalists believe. Since he sits on the court and you don’t.... and never will, his opinion carries more weight.
As for Scalia... as an American citizen-voter, I have authority over all those people in Washington. All I have to do is convince, or join, a large enough number of fellow-citizens who share my opinion.
“But SC justices aren't elected!”
I bet if enough Americans got together to demand it, they'd find a way to change all kinds of stuff about the SC, including the people on it, and without running afoul of the Constitution.