They may be able to pick a more radical Justice, depending on Senate Confirmation. On that I will agree. BUT, my point is that the present makeup of the court is 5 to 4 as far as idealogy goes. It doesn't make any difference who the 5 radical left wing Justices are, and Ginsburg is one in my opinion, or how radical they are. Replacing one radical with another will not change the make up of the court as far as that 5 to 4 idealogical split exist.
That is why right now Justice Kennedy is so important in the Court. He is the one who is most likely to vote either way on an issue, which he did on the 2nd Amendment voting with the Constitutionist on the Court on that issue. He right now is the swing voter.
Now if you were to replace one of those 5 radicals with a Constitutional/Originalist, or one of the 4 Conservatives with a radical left wing socialist, then you have changed the makeup of the court.
That was my point. Whoever replaces Ginsburg, no matter how radical they are, will not materially change that makeup of the Court. The problem is that whoever replaces, lets say Ginsburg, will hold that seat for the next 20 to 30 years probably.
Now, If Our President Obama decides to load the court with lets say a dozen more judges, like Franklin D. Roosevelt did when he up the number of Justices on the court from 5 to 9 in the 1930's, then we have a problem.