Indeed. Justices are expected to serve “in good behavior” indicating they can be impeached which is a power granted to congress. Size of the court isn’t spelled out in the constitution and the court has been different sizes as well. Maybe Alito would like to be part of a 51 person court. The power of the purse lies with congress. Alito might enjoy hearing cases inside of the local Denny’s if they can beat the brunch crowd.
And then there is the whole judicial review thing - this is the vast majority of the court’s power these days, and it has no constitutional basis. It’s allowed only because everyone went along with it. What if the court declared something unconstitutional and everyone just went “ok boomer” and didn’t give a shit?