"The dissent suggests that Congress cannot fend for itself... [but] Congress can tailor its sanctions to the gravity of the Executive Branch’s offense."

"A congressional inquiry may begin and end with a polite request for information. Or a chamber of Congress may escalate by, say, issuing a formal subpoena, threatening to withhold appropriations, or passing articles of impeachment. By the same token, the Executive Branch’s interest in reaching a mutually agreeable compromise should grow as Congress turns up the heat.... This political process also offers an array of possible resolutions in interbranch disputes—a diverse set of compromises and accommodations. For instance, the Executive Branch might agree to waive executive privilege if the Legislative Branch narrows its document request. Or if the dispute concerns an official’s testimony, the Executive Branch might agree to allow an official to answer written interrogatories or to testify in private.... The dissent’s approach would eliminate this dynamic system of escalating political sanctions and flexible settlements. When a lawsuit is the end-game of any interbranch dispute, the response to an overbroad subpoena isn’t 'Let’s talk' but 'We’ll see you in court.' And the resolution of such a dispute isn’t a negotiated compromise—one that leaves everyone a little dissatisfied—but a rigid judicial judgment.."

From D.C. Circuit the majority opinion (PDF) in the case of the House Judiciary Committee against former White House Counsel Don McGahn. President Trump claimed an absolute privilege to bar McGahn from testifying, and the Committee attempted to use the court to enforce its subpoena. You remember that during the impeachment trial, Trump's lawyers argued that it was wrong to accuse him of obstruction of Congress when the House had not gone to the courts to get an authoritative answer to the question whether he really did have the executive privilege he claimed. Now, at least according to this 3-judge panel, we can see that the judiciary would not resolve the dispute because the House committee does not have the standing that would make this a real "case or controversy" within the meaning of the "judicial power" defined in Article III of the Constitution.

We didn't get any sort of answer to the question what is the scope of executive privilege. The court is defining its own role, and even though a lot of people, during the impeachment proceedings, seemed to think that it's exactly the court's role to say what the law is and let us know how much executive privilege the President has and whether his resistance to Congress was a lofty protection of the power of the Executive Branch or a scurrilous thwarting of the power of the Legislative Branch, the court stopped at the threshold question of the power of the Judicial Branch.

No standing. That's a constitutional decision and it is — as the 2 circuit court judges said — not susceptible to a balancing test about how much we want or could benefit from an answer to the question. The part I quoted above works to say... and that's okay. The court follows a strict standing analysis because it's constitutional law and because it's better this way. It's better because it will be resolved through political back and forth. Interestingly enough, the tools of that political process include impeachment:

[A] chamber of Congress may escalate by, say, issuing a formal subpoena, threatening to withhold appropriations, or passing articles of impeachment.