That's the thing, though: this is fiction, which means (to me, anyway), that if those dozens of different artists are going to play in this fictional playground, the least they could do (in my opinion) is to do their homework in regards to what there is to know about the era in question.
That means getting the broad strokes, understanding the story and the important stuff. It does NOT mean that you're forbidden to introduce your own artistic variations. Compare all the various Andorian designs over the decades. They all get the basics right -- blue skin, white hair, antennae. But each makeup designer has brought their own individual artistic interpretation to that design, just as every comic-book artist who's drawn Peter Parker or Wonder Woman has rendered the character's face in their own individual style rather than exactly copying what their predecessors did.
As a Star Trek novel writer, you yourself do tons of research into the story you plan to write so you can be as accurate as possible to the source material.
Yes, but I still write it in my own style. I don't try to copy anyone else's approach, and my way of writing Trek is different from others', in that I take a more hard-SF approach, for one thing. The books I write are in my own individual style and voice. They're not generic
Star Trek books, they're Christopher L. Bennett books that happen to be about
Star Trek.
And hell, I change a lot of the source material. I stay true to the literal text, but I've often substantially reinterpreted the underlying meaning of a thing from what was claimed in the episode, or revealed that it was actually something different from what it appeared to be. I take the raw material and make it my own.
Ultimately, this is about being
creative. It's not just about facts or details. It's not about getting the right answer on a test or something. It's about people using their imagination and talent to create interesting things, to bring their own personal style to their work. The details are just the raw material we use to create with. They're the start of the process, not the end goal.
You don't write a story that completely contradicts the fictional universe of the show you're writing about.
It is ludicrous hyperbole to say that changing a few superficial details constitutes "complete contradiction." If it has a saucer and nacelles, if it has warp drive and transporters, then it's a Starfleet design, regardless of the exact shape of the nacelles or whatever.