The first answer to "why didn't you address the 24th" is that the Plaintiffs themselves didn't.
The authors don't mention having reviewed the Second Amended Complaint that was filed in the District Court. I did. It's available here: <link>
It raises claims under the First and Fourteenth Amendment, and then some statutory claims. In the midst of the 14th Amendment portion of the Complaint, it says that the burden imposed by the ID law is "akin to a poll tax."
But if I file a negligence case against a drunk driver and argue that the Defendant's activities were "akin to an assault" or "akin to murder," that's not enough to actually raise a claim for assault or murder.
You could look on the page I've linked and find all of the briefs filed at every level by the Plaintiffs. I'd venture to say they never actually argued that this law is a poll tax and never actually argued that the 24th Amendment actually should have been applied.
The modern Supreme Court only reaches out and makes or considers arguments not raised and preserved by the parties when it suits a right-wing ideological agenda to do so. This of course is not such a time.
The second answer is that the Supreme Court most certainly did address the argument that the ID law should be subjected to the same high standard applied to poll taxes. The lead opinion rejects that argument on the ground that the ID requirement is rationally related to the voter's qualification to vote (i.e., reliably establishing residency and identity). Having enough money to pay a poll tax is not rationally related to the voter's qualification to vote. Harman says only that if you have a poll tax, and the only exception is to prove your residency, the exception is too burdensome to save the tax.
Harman does not say that no burden can be placed on the right to vote.
And there, ladies and gentlemen, is the true answer to the question "when is something akin enough to a poll tax that the strict prohibition contained in the 24th Amendment will be applied to it?" The answer is, "a prerequisite for voting will be subjected to the rule of the 24th Amendment when the requirement is not rationally related to the voter's qualification to vote."
Harman, which you chide the Court for ignoring, is a 24th Amendment case. This one isn't.
So much for your two-page article.