Austria's system was created in the mid 1700s and would have been relatively new at the time of the founding. Was Austria's system clearly vastly superior at the turn of the 19th century?
Their separate constitutional court didn't come along until the 20th century[1]. They have 14 justices on that court, but only a maximum of 9 will ever hear a case for precedent-setting decisions, and usually fewer than that (making court packing difficult if not completely pointless).
They have always done what the US should do: keep the votes on a judgment private, so opinions speak for the court as a whole, and they don't let the losers have a soapbox by publishing dissents.
As a cherry on top, they enforce a mandatory retirement age of 70.
These factors make their court an actually apolitical body in a way that's in hilariously stark contrat to the US court. The US court is what you'd make if your entire goal was to turn all its judgments into political theatre.