Regulars are more expensive than recurring characters. I do believe there were budgetary reasons for axing a character if they brought on a new regular. And I can see why they wanted to try a new character. Rewriting the characters in an episode (like turning Bashir from an ordinary if unpleasant physician into a genetically engineered physician) is not very good writing in a show that has any use for character consistency.
I believe this because to my eyes Voyager skimped an awful lot. We mostly didn't notice because one of the writers' main goals was to cover it up. (Between things like that and the number one priority of fitting in commercial breaks, is it really any wonder that the writing for network television can be so frustrating for the viewer?)
Yes, Dax is a good comparison. I loathed
Dax, a loathing sealed by the episode Dax. I didn't loathe Kes because, let's face it, only because I liked Jennifer Lien.
Yes, Seven of Nine was a good bit of a Mary Sue. But unlike Kes, she didn't always win because everyone loved her and was awed by her native genius. She could at least be a suffering hero fantasy. Seven was a grotesquely schizophrenic character which gave her more variety than Kes. (Yes, that's supposed to be Janeway but that's just what the jutnobs say.)
Even psychic powers that were under control would have been bad for the show. For one thing, they would have been home by the end of the third season. That's bad, because, nothwithstanding fanboy/Ron D. Moore BS, the show wasn't a survivalist epic/Lord of the Flies clichefest, it was modeled on the Odyssey. The end of the story is getting home. The rest, is incident. (Vide Aristotle's Poetics.) For another, Kes winning everything isn't very interesting dramatically. And lastly, why does Kes hang around Voyager? Psychically superpowered Kes surely has better things to do!
And again, the Kes character, despite Lien's charm, had a gap. We don't know why she was there. Which is the sort of dramatic weakness that led me to speculate about dumping Paris (Gary Stu!) and Torres. We don't know why Paris is such a supposed bad boy or loser or rebel, especially since he's none of those things on screen. We don't know why Torres is so insane as to buy into Klingonism when Klingonism would put her down at the bottom.
Kim, as the male ingenue, may not be a fun figure for vicarious identification. And Kim, as the one delegated to piss and moan about being lost, may also not be fun to identify with. And he spent a lot of time as a cardboard cutout spouting the jargon to move the plot along. But on one level Kim has a distinct character with identifiable motives. You know who he is, even if you don't like to daydream about him. You could say the same sort of things about Tuvok and Neelix and even Chakotay.
But Kes and Paris and Torres were blank
cardboard cutouts. Perhaps it fostered vicarious identification if you could project a little bit of yourself into the blanks. But I don't think it was good writing. And I do believe that it is hard to keep writing about characters while dodging around what they want, why they're where they are, where they intend to go.
Yes, Lien was very charming in practically everything she did, because practically everything that was written for her was about how charming Kes was. The Darkling was catastrophic because we don't know why Kes stayed, nor do we know why Kes dumped Neelix, any more than we know why she took up with him in the first place. Cold Fire was pointless because we already knew that Kes had a perfect heart and couldn't succumb to the temptations of power. I really do see problems with writing for Kes and don't think the producers were just making pointless lies. I can believe that Ken Biller thought she was great, because I think Ken Biller is the biggest hack writer on Voyager.
And I will repeat, I think they would have fired Wang if the People poll hadn't highlighted the actor. Hiring a token was bad enough, but dumping on him would have been embarrassing.