It's been 6 years since Nemesis and we've had very few stories on the enterprise. Perhaps 1 or 2 per year. Characters have moved on, but as far as the reader goes it's still in the first season of stories, and unlike S1 of TNG there aren't books dedicated to whoever the security chief is now. The pre destiny book characters were wiped out, then Choudry went. It does feel that new characters stick around for about 30 pages of time before vanishing.
Voyager has done well I think as circumstances conspired to keep almost all the crew together. DS9 started well, but only really has Quark left now. TNG has hung on to most of the main characters too which helps.
For me this is the problem I have with current TNG. There have been far more TNG-relaunch novels than VGR-relaunch novels since Nemesis came out, yet I feel I have made a greater connection to new characters in VGR than in TNG. The new TNG characters seem so bland and part of the background compared to the VGR characters. It doesn't help that there is such a high death rate on the E-E that at this point I feel there is no point getting attached to the characters because in a book or two they will be gone. With the VGR novels sometimes I enjoy the sections set on the other ships with the new characters rather than sections with the characters from the show.
I think people don't like Chen because she is probably the only developed new character on the E-E, and therefore she has an actual personality and is a "character" which gives people reasons to either like her or dislike her.
I will stick with the TNG books as it was my favourite tv series and I do hope that the books get better, but at the moment I would rank the book series behind VGR, ENT and DS9.
Just my two cents.