I think we are misunderstanding each other. I'm happy about the variety of prose styles and plotting styles and pacing styles in Trek Lit. However, I prefer far less variety in the style of interpretation that an author brings to an established universe. I prefer tie-in fiction with less "freedom to interpret" and more established canon. I do not come to Trek for a wide variation of interpretations, but rather for more of a singular vision (well, at least TNG and DS9 levels of coherency). Frankly, if I want to read some really out-there and different science fiction ideas, I don't go to Trek. I go to Trek when I want Trek. Trek can have some out there and different stuff, but for me to love it, it needs to be Trek first and foremost.
I'm just trying to offer some historical perspective. I don't know how long ago you came to Trek, but what I'm saying is that the perception modern audiences have of what defines "Trek" is more clearly delineated in the wake of TNG, DS9, VGR, ENT, and the movies. But back when it was just 79 standalone episodes of TOS and 22 of TAS, plus two or three movies, the very nature and identity of the universe was less clearly defined. So the definition of what "Trek" was could vary a lot from person to person. I'm not saying you're wrong to have your preferences, I'm just trying to place it in historical context and explain why the older books had a wider range of approaches. The Trek universe was so much smaller and emptier and vaguer that there was much more room for individual interpretations of just what that universe was beyond what little we'd seen of it. As far as anyone knew at the time, Diane Duane's version of the universe or Vonda McIntyre's version or Alan Dean Foster's version or even Sondra Marshak & Myrna Culbreath's version was as plausible a take on the universe as anything else.