The Enterprise as it's featured in DiscoveryImage: CBS
The finale of Star Trek: Discovery gave us a short glimpse at the most legendary ship in the entire Starfleet: the Enterprise, ten years before the original Star Trek television show. Befitting the different visual style of Discovery, the ship looks a little different than we remembered, but that apparently wasn't just for creative reasons.
(Trek Movie has a great comparison of the two designs.)
Taking to Facebook to discuss the release of a calendar featuring an early design of the Discovery version, show designer John Eaves explained a bit about the process.
"Back in April of 2017 the task of the Enterprise making an appearance came to be and work was to start right away," Eaves explained (with some of the grammar modified for readability).
"The task started with the guideline that the Enterprise for Discovery had to be 25% different, otherwise production would have most likely been able to use the original design from the 60's. But that couldn't happen so we took Jefferies' original concepts and with great care tried to be as faithful as possible. We had the advantage of a ten-year gap in Trek history to retro the ship a bit with elements that could be removed and replaced somewhere in the time frame of Discovery and the Original series."
That guideline, apparently, came from legal, as Eaves went on to explain in a comment below the main post.
"After Enterprise, properties of Star Trek ownership changed hands and was divided, so what was able to cross TV shows up to that point changed and a lot of the crossover was no longer allowed," he said.
"That is why when JJ [Abrams]'s movie came along everything had to be different. The alternate universe concept was what really made that movie happen in a way as to not cross the new boundaries and give Trek a new footing to continue."
So that explains it. Creativity is shaped by constraints, after all. And I for one think the new old version of the Enterprise looks awfully sharp, all things considered.