That's not actually true, there's a lot of mechanisms that handle unconstitutional edicts.

The most important is basically forcing the issue into the political arena. If judges refuse to abide by a law, that law has no teeth. As a Liberal Republic, we want to prevent the law from being abided as default, so that it only becomes a hot-button political issue if the people put sever enough pressure on it to make the judiciary pay attention. But let's say the courts are wrong and they should start abiding by this new law they decided isn't constitutional. Both the executive and legislative branches have mechanisms of influencing the judiciary branch through appointments and finance. Additionally, if the executive branch doesn't co-operate with the judiciary, the judges aren't going to find anything to even rule on in general, which is going to cause more political pressure.

Additionally, a republican system is particularly useful for the interwoven judiciaries. The other courts can abide by the rule if need be, causing more pressure on the judiciary that's refusing it to comply, or at least for the problem to be passed back to the legislature which can clarify or assert the law, or the executives that hit the judicial appointments.

Okay, but what should the other branches do if congress passes an unconstitutional law? Refuse to convict, refuse to enforce, and pardon anyone that was alleged to have violated this law.

This is exactly what happened under Jefferson around the same time as Marbury v. Madison. The Federalist congress passed the "Alien & Sedition Acts" which, in one controversial section, criminalized disparaging the President of the US. Well, the Anti-Federalists & Democratic Republicans exploded on this issue along with all the other crazy shit the Federalists were doing, and it's one of the major reasons that Jefferson was put up to run as President. John Adams, unfortunately, believed too much in political representation, and didn't think that he should have over-rode the federalist congress since they represented the will of the people, while the Democratic-Republicans were getting fucking arrested. Literally newspaper's getting shut down and DR's getting imprisoned for disparaging Adams. This is why they called him a fucking hermaphrodite.

All the federal courts could really do was chose to abide by the law or not. Considering that the Chief Justice was very much an authoritarian (the guy who wrote the majority opinion in Marbury), it seemed like the courts were going to continue imprisoning opposition to the Federalists.

Well, in order to get elected, Jefferson promised to use the presidential pardon power to annul every single conviction under the law. The D-R's promised to remove or change the law as well if elected to congress. Under this pretense, they were elected. Rather than risk the law going through SCOTUS, Jefferson pardoned all the jailed D-R activists, journalists, and propagandists that the Federalists had rounded up. Then he refused to enforce the law until it was changed by the D-R majority congress, which it was.

At no point did it go through SCOTUS for review. Jefferson was probably concerned that the courts might all start to agree that politicians couldn't be criticized, particularly the Chief Justice of the Supreme Court. The Federalists were never in power again, and Alexander Hamilton (correctly) got his ass shot as he so richly deserved.

The lesson here is that if a law is unconstitutional, the first response to it is NOT a lawsuit and going to court. The first response is NON COMPLIANCE. Thanks to a republican system, there are all kinds of ways non-compliance comes first and the other government departments, agendas, and structures can refuse to act. Otherwise, you are effectively being governed by SCOTUS, and they have repeatedly made some of the single most devastating political decisions in American history. Including, but not limited to, effectively causing the American Civil War, legalizing eugenics and mass sterilization, allowing for the mass interment of American citizens in violation of their 4th & 5th amendment rights, and allowing the government to confiscate all private gold and silver supplies. These idiots are not to be trusted. No decision is better than a decision.

Take the reverse situation under Donald Trump. Look at what the other branches were able to do whenever Trump so much as breathed. Open defiance from every state government, open defiance from every governmental agency, mass lawsuits in every direction, open defiance after being ordered to obey the law, and not one person faced a consequence when they were asked to do the job they were appointed to do.

The Left is prepared to do exactly what Jefferson did and a hell of a lot more to stop anyone from stepping in front of their agenda. The courts have done nothing to stop them from violating the first five amendments, even to the point of unrestricted mass injection, mass house arrest, refusal to allow the policing of the national border, and political imprisonment. The courts have dragged their feet to make any attempt to restrict the power of the state, and when the Minnesota governor's unconstitutional edicts were rescinded by her own supreme court, she said she'd find another way to enforce them regardless of what the court even thought.

The political right in this country has been willing to accept every single decision that might be made by the Left-leaning courts, and lose ground on every issue regardless of the cost in lives or freedoms, and the Left is not prepared to even concede that your children shouldn't be chemically castrated without your consent. They do this for a ridiculous "Law and Order" idea that the people who enforce the law have no discretion in it's enforcement, despite that being the claim that was mocked in the Nuremberg Trial, and despite the fact that discretion is a primary part of both the executive and judicial branches. So, they stupidly wait for activist judges, who have done almost nothing to even slow the Left down. What you need are right wing people to do exactly what Jefferson did and say: "Nope. I don't enforce unconstitutional edicts. Full pardons on all these people. No enforcement of this law. No co-operation with a court that allows for it."

Otherwise, SCOTUS just nullifies congress, and it considered "balanced" to over rule 5 people with constitutional amendment, which those same 5 people have the unlimited right to re-interpret and re-define. "What even is the militia? Who needs bear arms?"