Replacing the court every four years wouldn't be that bad if the courts were more efficient. As it stands, however, cases can take over a decade during which any such SCOTUS rulings could flip flop entirely, resulting in legal chaos (which would be bad).

Change isn't necessarily a bad thing... Imagine if we had a new court every four years and one of them behaved like the current SCOTUS, overturning over a hundred years of precedent basically every chance they get. The damage could be undone just as quickly.