Earlier quoted context omitted.
They are limiting the ability of the government to make and enforce laws. The EPA is created with Congressional authority and is empowered to act on their behalf. Castrating the federal government will have negative repercussions. If the federal government doesn't have the power to control the states, then why bother having one?
They do, they just need to make laws that EPA can enforce. Not let EPA to act on its own. Isn't everyone always talking about unelected burecrauts going against the will of the people?
Its some weird Schroedinger's legislature, where it is legally empowered to direct the executive, it chooses not to, and somehow, that choice is the executive's fault, and we need an activist judge to rescue us from it. Instead, of the normal process of 'if the legislature is unhappy with the direction of the executive, it could just issue a course-correction by passing a law'.
The republicans know they can't pass that law right now, so they are using the courts to avoid having to pass it. Then they'll seize control of the legislature in the midterms, and they won't need to pass it. The beauty of having a stacked court, is that you can sit around and do nothing, and not have to write any unpopular legislature, while you sit around and lay all the blame for any consequences of bad governance on appointed-for-life judges.