it sounds like you're overlooking that deference to administrations is a double-edged sword.
Really, this isn't about what courts do as it's about what presidents do. Should a president be able to reinterpret laws at will? What of the next time a president reinterprets a climate law to say he doesn't have to regulate pollution?
These justices are trying to rein that in, saying that presidents really do have to follow the laws as Congress passes them, without such reinterpretation.