No, that's the core issue. They are overstepping the authority granted in legislation. If Congress passes an open-ended law saying "Agency X can administer Y in accordance with rules 1,2,3" then the agency should not be able to simply decide that rules 4,5,6 should also be created. This is what has been happening for decades, has been defended by Chevron, and is being forbidden by this decision.
How is the supreme court beholden to citizenry? They have life appointments, they're beholden to no one (except exceedingly rich "friends" apparently)