I was looking forward to Kes before the show started. Then the writers missed the whole point of her. She was a great way to tell stories about aging and facing death. You could start with her seeing life through the optimism and hopes of a teenager and end the series wise, calm, reflective. But instad they just used her for telepathy stories. Her major contribution was helping the Doctor gain his humanity; and the Doctor was the highligh of VOY to me in how he explored growing pains and obtaining a sense of identity.
Same with Neelix. Neelix was filled with regrets and bitterness but you rarely saw that side. They made him into the ship's clown and irrepresible happy go lucky guy. Neelix shined when he had to face the deaths of his family or prove he was not a coward, but those instance were few and far between.
I have heard the big problems with Chakotay and Kim were Beltran and Wang were unreliable and unprofessional. I guess with them and Lien, the bigger question is, "Did producers drop the ball during casting?" They sure did in their first attempt to cast Janeway.