None of those, however, contradict science, let alone logic, or the heart of the show that things will get better. (And quite frankly, they are NOT fantasy, at all, they are SCIENCE FICTION.) Fantasy is an entirely different thing.
A ship built on the ground however, violates all of that indeed.
Even if one grants that building a starship on the ground is needlessly inefficient, that in no way suggests that it's implausible. Many inefficiencies exist in modern naval shipbuilding that are tolerated and indeed encouraged in order to maintain a broad industrial base that can respond to increased shipbuilding requirements in times of war and continue to function in the event that certain facilities are destroyed.
And in 23rd century, space would be housing such a broad industrial base. Hell, we're readying to put such a broad industrial base in space today.
But, even that, is no argument, why not? So, where is this broad industrial base? Where are all the other ships in construction? Where is he massive fleet yard of hundreds if not thousands of ships that make up this broad industrial base?
It's just one ship, one construction site, in an isolated Iowan grass field friend.
Further, for there to be no such broad industrial base in space, it requires one of two or both requirements:
1. A collective irrational fear of space, and humanity wants to stay on a planet (which begs the question how we managed to colonized a 1,000 worlds and growing, or why we're even exploring, nobody would want to go (not to mention why we haven annihilated or attempted to every non-human species in sight)) showing a humanity that is totally uneducated; so uneducated, indeed, it practically has to be deliberate miss-education.
2. A collective apathy for anything to do with space, again humanity wants to stay on a planet (which gets us again to the same question).
Either option, is a DIStopia, a horror scenario for a future that I can't fathom, and is the exact opposite of what Star Trek is supposed to represent, it is taking the heart of what Star Trek is, rip it out, and trample beneath your feet.
Ok, so they decided in their story that because of futuristic building and launching practises, its more efficient to build the ship on the ground. I don't see how that's more of a leap than saying "luckily, for story purposes, an alien can mate with a human". Neither are particularly plausible, I grant you, but as you say, this is fiction, I don't see why one is fine and the other is a huge mistake.
Treknologicaly speaking

gravity hasnt been an inhibiting force in most of the trek ive seen on screen. Starfleet has had artificial gravity for a long time. Building ships on the ground should be SOP . When complete, just hit the AG switch and float her into orbit. I'd pay a few bucks to see something like that up close
The only thing that might violate the dreaded "C" word is that, if it's so easy ( and presumably efficient ) to build these huge ships on the ground, then why have huge space stations to maintain them? Having orbital "drydocks" and huge "Starbases" that can hold several starships inside them would seem to be an unneccessary expence when you could just float them down to the dirt side yards...
And this is the problem; if you had ANY understanding of what space is - and is not - you would understand that it is literally impossible for a ground construction and launch to be more efficient; as a part of that, safer.
In fact, all those futuristic building capabilities, makes the gap between building in space and building on ground, only BIGGER when it comes to efficiency and safety; not smaller, let alone that ground-construction would surpass space construction. (ESPECIALLY the safer one, space construction will always be safer, so much safer.)
It will never happen.
A ship built on the ground however, violates all of that indeed.
Folks at a NASA forum I am part of see no problem with it for the most part, and laugh at the "science" Star Trek has always passed off anyway. Therefore the ship being built on the ground violates nothing except some Trekkies assumption.
Then those folks are that NASA forum are idiots. Of course, that's something everyone with a little bit of knowledge of science and keeping up with things would know.
The average NASA guy (not mention most scientists) wouldn't know science if it hit them in the head.