Ascribing the flaws in FJ's work to a lack of passion is more than totally unsupported, it's barking up the wrong tree. If fans surpass FJ's work, there's basically only one reason and it has nothing to do with passion. The kind of passion you're evidently talking about would have demanded that publication of the book be delayed, perhaps to the point of being delayed indefinitely.
Franz Joseph Schnaubelt's lack of passion for Star Trek (and a higher degree of accuracy) is self-evident in the interviews FalTorPan has kindly archived and linked for us. I can't and won't try to find fault with this, because he clearly said that he wasn't a Star Trek fan but did prefer "Lost in Space". So whatever he did you take or leave it.
However, the way I remember the 1970's and its WW II publications it had been the golden age of cutaways (cutaway lines in red) and blueprints and I consumed these with great enthusiasm.
But even if you regard his Enterprise
deck plans as a free interpretation with artistic license, especially the engineering hull is a very poor presentation that reveals little or no effort to incorporate a credible infrastructure, IMHO.
The fact that the stem of the main sensor deflector practically ends nowhere but just above a swimming pool says a lot. I think he ran out of ideas what to put there and resorted to more crew quarters ("minimal quarters" for the stardrive crew according to The Making of Star Trek
that otherwise served as his guide what to illustrate),
another dance floor, another gymnasium, a rather large bowling alley and so on with plenty of redundant turbo shafts running through the hull.
So I feel there's also been a tremendous amount of lack of passion in that department.
Of course, the one good thing that came out of it is the inspiration to do better. But to do that, I don't think you really need years of research or CGI talents.