Yeah, Vorik didn't usually take much initiative. And simply because he was an ensign and would outrank all enlisted crew doesn't tell us his relationship vis-á-vis other engineering officers. It seemed there were quite a few officers there.
The best — only one that I recall — counterexample is in DS9: Starship Down, in which the engineering staff consisted entirely of enlisted technicians, not even true engineers. Worf was the only officer to direct them (and that was because he was the only officer stuck down there).
And Kim's rank of ensign was strange. He was explicitly referred to as a "senior officer" and all Ops people reported directly to him. That was highly unusual, I suspect. I can't believe that on a newly commisioned officer's first duty would be to run Ops on a significant vessel.
Harry acquitted himself so well, and so many officers died, that I have trouble accepting Janeway's rationale for never promoting him. How would it hurt to make him a lieutenant? Obviously she couldn't promote everyone to commander, but why not upgrade Kim?