If you read Chief Justice Roberts's majority opinion in 2019's
Rucho v. Common Cause (joined in full by the four other conservatives, all of whom are still on the Court), he specifically mentions the ways in which state legislatures have been restrained or outright bypassed by state constitutions and statutes and the states courts interpreting those accordingly:
The States, for example, are actively addressing the issue on a number of fronts. In 2015, the Supreme Court of Florida struck down that State’s congressional districting plan as a violation of the Fair Districts Amendment to the Florida Constitution. League of Women Voters of Florida v. Detzner, 172 So. 3d 363 (2015). The dissent wonders why we can’t do the same. See post, at 31. The answer is that there is no “Fair Districts Amendment” to the Federal Constitution. Provisions in state statutes and state constitutions can provide standards and guidance for state courts to apply. (We do not understand how the dissent can maintain that a provision saying that no districting plan “shall be drawn with the intent to favor or disfavor a political party” provides little guidance on the question. See post, at 31, n. 6.) Indeed, numerous other States are restricting partisan considerations in districting through legislation. One way they are doing so is by placing power to draw electoral districts in the hands of independent commissions. For example, in November 2018, voters in Colorado and Michigan approved constitutional amendments creating multimember commissions that will be responsible in whole or in part for creating and approving district maps for congressional and state legislative districts. See Colo. Const., Art. V, §§44, 46; Mich. Const., Art. IV, §6. Missouri is trying a different tack. Voters there overwhelmingly approved the creation of a new position—state demographer—to draw state legislative district lines. Mo. Const., Art. III, §3.
This is from the opinion of the Court just three and a half years ago. None of the other Justices in the majority took issue with it at the time and it's not like Justices such as Thomas or Gorsuch have any issue with writing a concurrence when they feel it necessary. There's precedent on top of precedent on top of precedent that should leave absolutely no runway for this theory to get off the ground.
The only exception for a state legislature to act contrary to its own constitution is Article V. I think the difference was noted by Solicitor General Prelogar when she was responding to Justices Kagan and Jackson. Justice Jackson was really focusing in on the fact that the law-making authority of a legislature is derived from its state constitution and that authority is subject to all of the checks and balances that may exist. When it comes to ratification (unlike the Elections Clause), that is not a law-making function, but rather a specific federal function (as the Court recognized a century ago).