One of the innovations in these court challenges was the "ensemble" method of producing thousands of plausible maps and doing statistics across likely outcomes of those maps. Kagan found that this demonstrated "the State’s map was an out-out-out-outlier" in the case of North Carolina's map which was worse than all 3000 other proposed maps it was compared to. Roberts mocked this claiming, "Judges not only have to pick the winner—they have to beat the point spread." Roberts at other points wanted to avoid such 'hypotheticals', but Kagan found that "... the same technologies and data that today facilitate extreme partisan gerrymanders also enable courts to discover them, ..." Kagan isn't afraid of technology, it's not some weird magic black box to her. It's a tool, and it's not some weird hypothetical, it's a tool actually used to create real and effective gerrymanders, and the same tools can analyze and pick apart those gerrymanders.
With great handwringing, Roberts repeatedly claimed that there was no solid rule on which to base a decision or decree a change. Kagan responds with a long list of citations of Supreme Court and other Federal Court decisions that found rules and made decrees.
Roberts implicitly suggested that Congress and State Legislatures could make laws creating such rules. He cited a list of bills relating to redistricting rules to which Kagan responded, "what all these bills have in common is that they are not laws. The politicians who benefit from partisan gerrymandering are unlikely to change partisan gerrymandering. And because those politicians maintain themselves in office through partisan gerrymandering, the chances for legislative reform are slight." (Emphasis Kagan's)
Kagan doesn't think we should wait for ballot initiatives either: "Fewer than half the States offer voters an opportunity to put initiatives to direct vote; in all the rest (including North Carolina and Maryland), voters are dependent on legislators to make electoral changes (which for all the reasons already given, they are unlikely to do)."
And on independent commissions, "Some Members of the majority, of course, once thought such initiatives unconstitutional. See Arizona State Legislature, 576 U. S., at ___ (ROBERTS, C. J., dissenting)"
Should we have Congress make a law restricting gerrymandering nationwide? Absolutely. We should have a new Voting Rights Act that ensures a fair process in every state. We should also have a Congress that will pass it and a President who will sign it.
We should also have a Court that will do their job. For over two hundred years the Supreme Court has been a check against bad laws. Gerrymandered district maps passed by state legislatures are bad laws. Instead of using their encyclopedic knowledge to write 32 pages of "we don't wanna" they should have done their duty to the Constitution and the people of the United States of America and defended our democracy.