To be clear, I have watched the show through the first 5 seasons since 2010, and I came away unsatisfied, feeling it was a waste of time to watch the show. DS9, by comparison, has aged well, as has TNG.
My complaints with the series begin with how it was started. If Voyager was a mission that reflected our needs in man-space-travel outside of the solar system (right now), where we had the infrastructure to grow our own food, raise and train our replacements, find a perpetual energy source, and did this by telling stories over the course of their mission (years, not just the first seven), I think the show would've avoided the TNG label and it would've been the same blank palate that the show wanted by going to the Delta Quadrant. Why would we sign up for such a mission? Because we are explorers. I think it would've been great if they had an engine to get to the Delta Quardrant, but not one that could get us back.
Even if they didn't do that, there's a lot of unexplored territory with the Maquis-Starfleet conflict. This is where the show could've shined. Having two different agendas would've been great for a post-DS9 show. But alas, it played for a season or two and was gone, and when it did play, it was more like two squabbling children, than the gravitas of two intelligent competing arguments. I think they didn't go dark enough with how the Maquis officers would want to start their own colony, etc.
My major complaint with Voyager is this--they did original stories. But their iconic moments were based on dealing with races we already met--especially the Borg. It was pop-culture Trek that relied on too many old faces. DS9 had "The Dominion," and gave relevance and re-defined the Cardassians, Ferengi, and the Bajorans. TNG had "The Borg." And even during the run of TNG, there were plenty of alien-of-the-week stories that stood on their own. Seven of Nine and Icheb, Seska is a Cardassian, etc all relied on knowledge of the Trek that had come before it. Like I said, Pop-culture Trek where they used what was popular, and never did anything that made me think "I understand the Cardassians better because of Seska," or "I understand the Borg better because of Seven of Nine." It was unoriginal during most of its run, and that made it a bland version that's not worth remembering.
The actors performances of the material was also bland. The Doctor and Kes aside, most others were not giving performances that were memorable in a good way, that caused me to have an emotional connection to the characters. I think Kate Mulgrew overplayed a lot of her scenes. I think she was a stereotype of a 90s woman in that role, as it was still new to have a woman leader. 20 years later, her performances look horrible. I think Robert Picardo is the only exception to what I am saying here.
I think the show had a lot of promise, and didn't do anything with the characters. They lacked intelligence and gravitas that the TNG characters had. Like it or hate it, you believed
the the TNG crew was this moral. There's something disingenuous and preachy about Voyager that I never liked.
That's where it lost me. I don't know about any others.