I've made the observation, the hill i'll die on for this topic, that Harry Kim actually wasn't cut out for Starfleet. Had he not been on Voyager, he wouldn't have lasted on a ship. He has consistent behavioral issues and has shown time and again to be completely willing to ignore or disobey orders when it benefits him personally to do so, and he tends to be erratic and emotionally driven, lacking discipline beyond even that of someone like Tom Paris and the Maquis crew.
Kim was Voyager's trouble maker. Janeway didn't promote him because he didn't deserve to be promoted. He was good at this job... as long as he actually obeying orders... and given their situation she needed to keep him in place, but in essentially any other situation, Kim would have been either sent to some low level position or kicked out of Starfleet entirely.
He's smart and good at what he does, but he's an absolutely maverick firebrand. That was supposed to be Paris, but by and large, Paris is the voice of reason to Kim's madness.
This isn't really a negative view of Kim, it's just an observation. While he "should" have been the model Starfleet officer, turns out... Starfleet actually probably isn't for him. That's ok, his talents can still be utilized.