Every time they had the opportunity to write something challenging and interesting, they wimped out and wrote something easy or ratings-inducing, whether it was scarce supplies (they weren't), a contentious Maquis crew (they were almost never shown) or a Doctor who isn't really alive (oh wait, he magically is!).
That's been my problem with Voyager as well. Judging the episodes alone, they're for the most part entertaining with the same occasional clunkers every show winds up with. However, when taken as a whole, it loses something.
Moreover, when things in an episode demand follow-up, they're usually ignored, not to mention the lack of build-up to these events - B'Elanna's suicidal depression in 'Extreme Risk,' I believe it was, for example, should have been built up and it should have been followed up - Star Trek has yet to have an episode that deals with the long term effects of depression, and the episode itself basically says that suicidal depression is something with a quick fix and you're all better. The only characters I can look at each year and say 'yes, they have been affected by the things they've been through this year' are the Doctor and Seven.
As a would-be-writer myself, I was particularly disappointed by the statements from Voyager's writers that they didn't do things with some characters because they weren't interested in them - Seven and the Doctor, as the ones developing their humanity are easy to write for. Someone like Harry, or Chakotay, or Neelix, or Tuvok, or Kes aren't as easy, they're people with pasts that predate the show that can have an effect on them. The Doctor had no individual traits until they activated him in 'Caretaker.' Seven spent most of her life among the Borg Collective, having been assimilated at a young age, so she had no real personality that reassurted itself after she was disconnected from the Collective. Those two are blank slates and can be and do what the writers want without them having to make it a part of their character - they're experimenting with this or that, and if the writers don't like it, they can say that the 'experiment concluded, and I have no further use for that activity.'
Voyager had the potential for a number of stories, experimenting with what happens to people pushed to the edge, and the psychological effects (I got into some of the things I would have liked to have seen on the show in the 'what would you have done different' thread). But they decided to keep things lighter and 'easily accessible,' so they didn't include the arcs, both character and plot driven, that I prefer in shows. It's not a bad decision - just not a decision that I agree with.