Its not that, its just a known dated styling. The whole thing screams 1960's. Trek itself revamped the ship and came up with a laughable excuse ( refit) that changed everything, including size and number of decks
They tried just updating the Textures ( on the outside) in though a mirror darkly, but they could not hide what it was. Its like a car, you know what decade its from by looking at it and it looks its age, no matter how you change it. This is not always bad, but it does mean you can not place a 68 Camaro , next to a 2017 one and call them the same decade. Sure they have a similar styling, but are clearly not from the same decade.
This is the Issue, the 1960's connie, will always look like a 1960's connie. Those designs are the sore thumb of trek because it moved away from that look at once. Nothing after TOS looks like that, Its out of place and even Gene was OK with decanonizing the whole thing.
Exactly. The only reason it LOOKS outdated is becasue we know it's from the sixties. Just becasue we think it looks outdated doesn't mean it really is. So there's no reason to redeign the ship just becasue our perception of it makes us think it looks outdated.
So what you do is you take it and rebuild it, you make it fit the post ENT look. Even a cleaned Up and retexturized TMP ship looks far more in line and fitting than a 60's era ship.
Not if you're setting your show in the time period when that design existed in universe.