Kes was a problem from the get-go. Those of her race only live nine years. She'd have to age (by human proportion) almost a decade a year. Add to that the whole giving birth from the back thing. I'm not prone to lying up at night wondering about this stuff, but there is just no way a being like that would look as human as she did. Then, she's telepathic. She's rapidly turning into a character that sounds like an entry in some Make Up A Character contest.
On top of that, the actress then develops an allergy to her makeup. Imagine if that had happened to Leonard Nimoy!
I liked the actress, but I really do wonder what they had in mind with that character, had things worked as they (presumably) planned...
Also, the whole Maquis thing. I'm of the opinion that a character or concept is best if it's basics can be described in one sentence. Imagine watching
Voyager with someone who doesn't watch
Star Trek. Imagine trying to answer their questions about this stuff without the feeling that for them this is just getting too involved to spend time on. I think this is a large part of the perception that
Star Trek is too weird to watch. Answering the question of "What's that thing over his eyes?", or "Why does he have pointed ears?" was one thing, those were easy to grasp. The Maquis thing I think was just too much, for I think even many of us weren't 100% fluent enough in it to answer. And for what little payoff there ended up being with them in the series, I really don't believe they were worth it.