I think the reason Herrmann's music isn't "dated" by contemporary standards is due to the repetitive minimalism of his style, which makes it not stand out as "corny" or "old-fashioned" in the current era of film music where every score has the same simplistic chugga-chugga string ostinato repeating endlessly. Other Golden Age composers like Steiner, Rozsa, Newman and the like tended to write long-line, melodic themes, and while Herrmann was certainly capable of writing in that style as well, his obsessive, repeating two and three-note motifs that play through scenes rather than mold themselves to specific character or visual beats looked forward to composers like Philip Glass, and wouldn't sound that out-of-place even in a modern blockbuster.
You might easily be right -- his proto-minimalism could definitely be a factor.
I remember a review of Einstein on the Beach that said that calling it an opera by Philip Glass instead of one by (director) Robert Wilson would be like calling Citizen Kane a film by Bernard Herrmann instead of by Orson Welles - except, the critic pointed out, that Herrmann was a far more inventive composer than Glass.
To tag on to this, much the same could be said about the ostinato driven and minimalist scores of Akira Ifukube. His original 1954 Godzilla music sounded fresh and exciting even in last year's Godzilla King of the Monsters.
Ifukube's stuff is also loaded with parallel fifths in the harmonies, which is of course the stuff that rock and roll and modern pop music are made of. That could play into it too.
Truth be told, even a lot of Rozsa's scores had that kind of obsessively repeating "cellular" structure, particularly in the tenser passages. His noir scores from the 40's have that same kind of Herrmann-style terseness that still play well today. Granted, he could also write some of the most beautiful, long-form music imaginable.
Coincidentally, I was listening to the Tadlow Ben-Hur last night and thinking about what an absolutely fantastic composer Miklos Rozsa was. (Of course, it's pretty much impossible to listen to Ben-Hur and not think about how remarkable Rozsa was and is).