Voyager's biggest sin can be summed up in two words: Wasted potential.
The idea behind the show was great for a nitty gritty show of two crews being forced to work together despite their differences in a hostile sector without support... instead we got rather regular "nebula with weird shit of the day" episodes that didn't really stand out as much as they could.
Neelix' character is the same problem, when you really think about it. Some dude who worked as a junk hauler after his home planet got turned into a wasteland with his family and friends dying terrible deaths... They exclusively used him as a comedy clown, but had they played up the serious moments a bit more to show that he's broken goods on the inside that just makes the best of his life, now that could have been great.
The episode where Neelix meets the guy that invented the weapon that destroyed his home planet. Even the episode where they bring him back from the dead is pretty cool. Neelix coming to terms with his post-death experience and all that stuff. Then the "Flight of the Phoenix" inspired episode with the spacelift, that one was great as well.
That were some great character moments.
Neelix' main role in other episodes was to just sorta be there, I think episodes that showcases that he knows how to pull through under even the worst conditions would have been cool and would have beefed up the importance of his character in a unique way. Episodes could be centred around the idea that Starfleet might be great when there's a spacedock around to get spareparts and support by an entire fleet of other Starfleet ships, but are a bit out of their league when that stuff is far away for too long. I imagine a storyarc where Voyager goes low on supplies, gets slowly whittled down by an enemy that they narrowly escape and Neelix, being the expert in improvisation that he is, has his moments where his input allows the crew to keep going and fight another day.
When you look into survival-guides by the military, there is always one lecture about valuing living. The idea being that mere survival is not enough, that you need to remind yourself *why* you need to stay alive. In many cases, survival depends not only on keeping yourself dry, warm, hydrated and fed, you also need to keep up mental strength and the will to survive.
That's what Neelix should have been for the crew, not just a clown that stirr-fries weird-looking vegetables in the background, but rather the guy that reminds people why they fight, why they strife and why they need to keep swinging, even if it's hard and painful. Dude watched his entire planet being consumed by a weapon of mass destruction with billions of lives being wiped out in an instant, he saw the direct aftermath. He went through hell and came out the other way not a miserable wreck, but rather someone who despite it all tries to find happiness.
He could have been one of Star Trek's greatest characters in that regard...
Instead, we got an underwhelming side character, that has his moments, but could have been better. I still like his character and never truly understood the levels of hatred he got, but like everything Voyager: The core idea was solid, it was just never truly used to its fullest.
