Posted this on a WONDER WOMAN forum-topic.
Some of the zeitgeist that made Wonder Woman able to sustain two features at once was a consequence of World War II boosterism. Both Wonder Woman and the Sub-Mariner were in part popular because even though they were not Americans, they made America's cause their own. In an inversion of the trope in which godlike Americans go to Europe to save the Allies, they're godlike Allies defending Americans and other Allies-- and Wonder Woman even drapes herself in the stars and stripes to reduce any sense of her "foreign-ness." It may not be a coincidence that neither character has enjoyed anything like the sales/popularity they once enjoyed.
Wonder Woman was also at her most popular when she was aimed at kids, the primary purchasers of comic books in the Golden Age. Her fame and the complexity of her original setup could make it possible for her to enjoy success with an older audience-- but it would have to be in a format that modern adults would buy, and that ain't the floppy magazine format.