I've considered myself a huge Trek fan for a good decade now. Although in the larger scheme of things, I'm still a dense smart-ass upstart when the more senior folks are concerned. Anyway, I always thought that the TMP era was the most cinematic visual aesthetic for Star Trek that has aged as well as the OT designs from Star Wars.
TMP movies had perfect balance of ship designs that seemed to be more focused on the engineering aspect rather than just looking cool. It was grand, detailed but also subdued at the same time. The Refit Connie, Miranda, Excelsior, etc. had the presence of mind not to overdo the excess glowy nacelles that would mark the next-gen era, and to an extent even the JJ movies and Disco.
When TMP came out in '79, Trek obviously played catch up with Star Wars. But Trek set itself apart with that "Starfleet clean" look as opposed to the grimy used up style that was gaining traction. Everything seemed to be very polished and top of the line but that was the point anyway! I guess Gene wanted to depict Starfleet space exploration like this grand event, calling back to the age of sail mixed with NASA for good measure.