I loved the early 80s "professionally written fanfic" - I totally remember those days. I remember several books where the author said "I worked on this novel throughout the 70s, I never thought it'd ever be published" or words to that effect.
The trouble was, by the late 80s / early-to-mid 90s the series was running on fumes. These same authors, when asked to write a second or third book with an actual deadline, it just wasn't as good as their initial novel which had been percolating for years as fanfic. Sometimes they'd be asked to write about characters in the 24th century that they clearly didn't care about, or (cough, cough Carey) were openly contemptuous of.
For a long time it felt like the trek novels were totally phoning it in, with a monotony of planet of the week TOS book one month, TNG the next. (And, after a while adding DS9, VOY, and ENT to the rotation and going to 2 books a month.)
It really was in the late 90s when they started taking chances, doing miniseries, adding new characters, and trying new things, when the books started getting good again. The Ordover / Palmieri era was when the novels started finally being worth reading every month. And of course I feel like today the books are better than ever before.
I think you do need to strike a balance between standalone planet-of-the-week stories (which are a staple of Star Trek) and ongoing narrative, and I feel like they have done a great job of that lately. For a while they trended too much towards ONLY arc-heavy stuff, but the pendulum has started to shift the other way.
Maybe that's what he means by a "hopeful trend" and he prefers old-school standalones?
Personally I like having a balance of both. I love the ongoing storyline and new characters, but I need a plain old planetary exploration adventure occasionally too. But I do not want to go back to the early 90s, with nothing but alternating planet-of-the-week standalones and static characters.
Its helped that they don't make them put all the toys back in the box every week now that the shows are all off the air. And of course the writers that have been circulating through for the past 10-15 years have been really good. I think that makes more of a difference than anything.