Okay, here's the dirty little secret of the tie-in business:
It doesn't matter who writes the books.
Yeah, I've read some awful tie in fiction, so I'd argue the author does matter actually. Thankfully Trek has mostly avoided that.
Speaking personally I DO shop as much based off the author as anything else. Just slapping 'Star Trek' on a book will not ensure I buy it.
I think you might be missing KRADS point though. You might be so discerning, but sales figures would apparently say something else. It's no coincidence that we constantly get Kirk, Spock, and Picard on book covers, even if they are relatively minor characters in any given book. It's the brand recognition that sells tie-in fiction to most people. So there wouldn't have been much point say, putting T'Ryssa Chen on the cover of The Struggle Within, because no one will recognise her - It's shooting yourself in your marketing foot.
Sure some authors make a difference, see the Laurell K Hamilton reprint a couple of years ago, or the Shatner books. But for the most part its the name Star Trek that drives the sale.
Heck, I'm guilty of it; I've bought recent Titan and Enterprise novels because I enjoy the series, and want to support the brand. Most definitely not because of the authorship!
The counter argument I suppose is that the brand recognition suffers if it is associated with a low quality product. But that's not really the case with Star Trek prose now is it? As much as I really want KRAD back in the club, I'm also really happy with almost all the current crop of regular authors.