My follow-up posts discusses this.
I just think Trek is a different beast when it comes to novels. I can read a generic novel and care about what's going on. But when it comes to Trek, I want to read about the characters I've loved for multiple decades now.
For me, a big part of picking up a Trek novel is the nostalgia factor.
Or, you're simply not letting yourself enjoy new characters.
Lots of fans rejected the idea of Saavik. And probably would have felt the same about Xon had "Phase II" gone ahead. Had the novels been ongoing series and movies, new characters would come and go. (Guinan and Ro Laren were pretty popular late additions to TNG.) And regulars would leave.