In looking at the design process of the TOS Enterprise, the only thing that struck me as retro in any way was the primary hull (which started out as a sphere, but ended up back towards a more C-57D design by August of 1964... most likely because it was supposed to land like the C-57D).
I, personally, don't see anything 60's about the TOS design any more than I see anything 60's about passenger jets today (who's form, or style, hasn't evolved at all since the 60's). In fact it is the lack of style (and how it moved away from the C-57D's esthetic) and became more and more utilitarian throughout the fall of 1964 that makes it iconic. Jefferies wanted everything to seem reasonable (even if reasons hadn't been attached) to everything about the ship. Of course the final design wasn't just by Jefferies (who was an assistant art director at that early stage), a lot of other people added influences (including Roddenberry).
And because the original process was rushed some of Jefferies favorite ideas about the design came after the models had been built. He put some of those ideas into his Klingon Battle Cruiser design, and then got the chance to introduce them to the Enterprise design in 1977 when he was asked to redesign it for Phase II. Most notable among the things he wanted changed was the engines.
The design eventually became the foundation of the TMP Enterprise. And I personally think that had the design stayed
dialed back (similar to how the model was originally built), it would have been a better design. The push for
art deco influences in the design are it's biggest detractors.
As for the new movie's version... I thought the original paintings by Church felt elegant and artistic. And in that it seemed like what we might have gotten for the TOS Enterprise had they not steered away from the influences of Forbidden Planet. But as a prequel to TOS, maybe the stronger connection to Forbidden Planet would have been appropriate. Sadly all that type of nuance was lost on the director who apparently wasn't aware of SciFi outside of Star Wars, so what started out going in an interesting direction went astray quite fast. The saddest aspect of the new Enterprise is she was an after thought in almost every respect (mostly because the people making the film didn't believe the audience would care... and they were proven right).
So yeah, I don't think much for (or about) the new Enterprise... and that was the way it was intended, so success all around.
