Exactly how would REPLACING the characters have made a difference without better writing? The characters didn't need replaced (except maybe Wang who realllly couldn't act), the writers just needed to get their sh*t together and find some direction for them and work on it and not just work on what the concept of the next episode would be.
Take Chakotay, for example. They essentially killed the drama inherent in his character in the first or second episode. After that, he became another version of Fat Riker. So, after the audience has watched him sit around doing paperwork for three seasons, are they suddenly going to believe he's once again a dashing rebel commander? It seemed like once the VOY writers made someone a boring putz, they were resolved to keep him a boring putz for the next 7 years.
Yeah, and the David Kelley reference is apropos. Most episodic dramas don't fear turning over their casts. Star Trek was lazy because they were immune to being cancelled.