4) The most interesting characters are the lowest ranked supporting characters
Well, this is the root of the problem. The issue is that the most interesting characters of the Voyager are those that haven’t been put in charge of anything. The passably interesting member of the ensemble is Garret Wang’s Ensign Kim. The receding hairline of Tom Paris is not very convincing as a ‘devil may care bad boy’. Moreover Paris has feelings for B’Elanna Torres, so there is something definitely wrong with him.
The best characters of the show are a holographic Doctor who is not even real (probably), and alien explorer who the makers have decided to hide behind a stove in the kitchen and a super-sexy Borg who lingers around in a cargo bay almost all her time.
The show later on realized the importance of those characters and introduced many episodes centered on them. But since they are not doing anything, it’s hard to give them a proper role to act.
Besides the inconsistent cast of characters, the Voyager faced much larger problems. One of which was they never really utilized the premise properly. It was rather an extremely good premise that could have rejuvenated the entire Star Trek universe.
Neither do they have resources, nor do they know where they are. Moreover half of the crew is killed and are replaced by a bunch of rebellious space pirates. Still the Voyager decides to do everything by the book. Those rebel marauders, the Marquis, are simply indistinguishable from every other Starfleet officer on the ship.
The writers of Voyager are more interested in spending the time on the holodeck rather than actually addressing the show’s premise. Instead of dealing with the real world, most of the shows involved dealing with the holographic worlds where the crew is busy in Klingon rituals or having sex with Irish bartenders. It’s not just the overuse of holodeck that created a mess; it is the overuse of every technology the writers thinks is a hit that has ruined it all. If a technology is exploited beyond measures, it starts losing its meaning.