That’s true. It’s not likely to happen. But they do have the power to abolish inferior courts, so in theory, they could scrap the current appellate and circuit courts and start all over, though such a sweeping overhaul has never been done before. Here’s an interesting article I found on the subject:
https://constitution.congress.gov/browse/essay/artIII-S1-8-5/ALDE_00013561/
Do you really expect the Supreme Court to take on all the day to day cases that happen in a federal District Court?
The Supreme Court only reviews about 100 cases each year.
The federal courts handle nearly 1 million cases each year at the District and Circuit levels.