With regard to whether or not a work is transformative, the Supreme Court’s formulation from Campbell v. Acuff-Rose, a case about parody, asks whether the new work merely supersedes the original, or instead adds something new, with a further purpose or different character, altering the first with new expression, meaning, or message.

A practical way to think about it is this:

What is the new use for? Courts look first at whether the secondary use serves a different purpose from the original, not just whether it looks different. Uses for criticism, commentary, parody, scholarship, search/indexing, or other new functions often have a stronger transformative argument.

Is there new expression, meaning, or message? That still matters, but after Warhol, a claimed new meaning by itself is usually not enough, especially when the secondary use is being exploited in a similar commercial market as the original. The Court emphasized that the inquiry is tied to the specific use at issue and whether that use has a distinct purpose.

Does it substitute for the original in the same market? Even if the new work has some new meaning, it looks less transformative if it is serving basically the same licensing or audience function as the original. That overlaps with factor 4 as well.

How much was taken, and was that amount justified by the new purpose? A use is more defensible when it takes only what is reasonably needed for the transformative aim. In parody, for example, some copying may be necessary to “conjure up” the original, but not more than needed.

All of which I think can fairly be evaluated in GN's favor. Though as you point out, the lawyers are paid to argue each point.