I think that it's a lame excuse from those in charge. If the character "didn't go anywhere", then how could they come up with good stories about that character up to the last possible minutes of season 3?
As much as
you love her, the character was ill-conceived. An alien who had a five-, then seven-, then nine-year lifespan (presumably so she could reach old age if the series went seven years), and came from the other side of the galaxy, but looked human with pixie ears. An actress with gorgeous, long, blond hair hidden under a wig that, in the pilot, resembled a mop head. She was in a relationship with Neelix, who called her "beloved" - and yet Kes didn't enter puberty until "Elogium"!
Why did they lose their ability to write for the character exactly between season 3 and 4
The writing was on the wall very early, hence the breakup (offscreen!) with Neelix.
Not to mention that Jeri Taylor could come up with at least one good kes story after Kes was gone (the one in the book "Pathways".
That book was written much earlier, but was delayed many months, because Paramount insisted that all new novels
reflect the addition of Seven of Nine to the crew, so Taylor had to rewrite the prologue and epilogue - and Neelix had to magically channel the spirit of the departed Kes to tell her already-written origin story - to get it published.
If Kes was ill-conceived, then most of the characters in TOS, TNG, DS9 and Voyager are ill-conceived too. Not to mention that bunch of wood spoons in ENT and the third-rate TOS clones in the NuTrek movies.
I agree that the life-span was silly, a stupid attempt of the writers to come up with something Star trek never had had before. But it could easily have been changed by giving her a prolonged life-span, something whic was possible according to the episode "Cold Fire". As a matter of fact, it took me five minutes to sort that out in a story I wrote (not to mention the one minute it took to sort out the crap from that horrible episode in season 6) and if an amateur like me can do that then a professional writer is expected to do it too.
As for humanoids from the other side of the galaxy, well in Star Trek almost all characters look human even if they are from the Andromeda galaxy.
Nothing wrong with a pixie haircut and pointed ears. We have had pixies before (Ezri Dax), pointed ears (Vulcans and Romulans). We have had half-Klingons with ridged foreheads, not to mention females with biig boobs in catsuits (on a spaceship where the crew are supposed to wear uniforms). As for Kes's hair in the first episode, it looked far better than most of the boring hairstyles that female characters are supposed to have on a Federation starship.
As for the break-up with Neelix, it had nothing to do with Kes being shoved out. It was just a logical step because the relation was more and less over since season 2 when the writers must have realized that it didn't work. Unfortunately, they weren't able to come up with a decent breakup. So much for their skills.
In fact, the break-up looked more like a new beginning for Kes than an end.
Not to mention that Kim was the one who they planned to dump, not Kes.
As for Taylor's novel, it still proves that she was able to come up with good Kes stories in season 3, not to mention that Kes had more and better stories in that season than Kim, Neelix and even Tuvok. As for the re-writing of the book, well the dictatorship and Seven worship affected even the people at the top of the nomenklatura.
Maybe I should have thought about it when I tried to sell my idea for a book, it was about the wrong character.