"The decision merely says that 'state courts do not have free rein' and that they may not 'transgress the ordinary bounds of judicial review...'"

"'... such that they arrogate to themselves the power vested in state legislatures to regulate federal elections.' The court offers no concrete understanding nor any example of what that means. It’s clear that a majority was cobbled together among conservative and liberal justices by agreeing to decide this part of the case in the narrowest terms.... [T]he state court interpreted general provisions in the state constitution — such as that requiring elections to be 'free and fair' — to in effect ban partisan gerrymandering. Whether this decision transgresses ordinary judicial review or exemplifies it remains a mystery. Had the court resolved that question, it would have provided much-needed guidance for 2024.... Judicial minimalism can be a virtue in many contexts.... But in the context of election law, it can be a vice. Elections benefit greatly from clear rules laid out well in advance of Election Day.... Clear rules specified in advance are all the more important in this era of pervasive distrust and suspicion concerning elections...."

Writes lawprof Richard H. Pildes in "The Supreme Court Rejected a Dangerous Elections Theory. But It’s Not All Good News" (NYT).

The love for clear rules is easier to express after the Court has rejected the clear rule your opponents were pushing. 

ADDED: Pildes declines to mention Bush v. Gore, but that's the precedent here. From the majority opinion in yesterday's case, Moore v. Harper:

"So to uphold direct democracy as a constitutionally permissible tool for regulating elections, the court had to conclude that, when the Constitution uses the term 'legislature'..."

"... it does not (in its original formulation) permit the popular election of senators but does permit popular regulation of the election process. There is no easy answer, and that conundrum is what produced a legitimate 5-to-4 divide," writes lawprof Richard Pildes in a NYT op-ed about the opinion in Arizona State Legislature v. Arizona Independent Redistricting Commission.

[T]o uphold direct democracy as a constitutionally permissible tool for regulating elections, the court had to conclude that, when the Constitution uses the term “legislature,” it does not (in its original formulation) permit the popular election of senators but does permit popular regulation of the election process. There is no easy answer, and that conundrum is what produced a legitimate 5-to-4 divide....

The main, and best, justification for direct democracy is precisely the need for this kind of check... on the self-interested temptations of power when legislators regulate the political process itself.... Direct democracy is hardly a panacea or a pure expression of “the popular will,” whatever that means; voters must be organized and informed, which takes resources and organizational skill. Still, direct democracy remains an important means of policing the inevitable temptations those in power have to entrench themselves more securely in power.

I haven't read the opinion yet, but I've long thought that direct democracy is unconstitutional, for reasons the Court disposes of in footnote 3:

The people’s sovereign right to incorporate themselves into a State’s lawmaking apparatus, by reserving for themselves the power to adopt laws and to veto measures passed by elected representatives, is one this Court has ranked a nonjusticiable political matter. Pacific States Telephone & Telegraph Co. v. Oregon, 223 U. S. 118 (1912) (rejecting challenge to referendum mounted under Article IV, §4’s undertaking by the United States to “guarantee to every State in th[e] Union a Repub­lican Form of Government”). But see New York v. United States, 505 U. S. 144, 185 (1992) (“[P]erhaps not all claims under the Guarantee Clause present nonjusticiable political questions.”).

I'll get back to you when I see how close anybody on the Supreme Court got to what I think is the answer. I hope this Pildes appetizer will tide you over.