Star Trek: Voyager is a great show. It's one of the best shows not only in the franchise's canon but also in the history of science fiction television. It's an incredible journey that lasted for seven seasons and focused on two crews acting as one to get back home. It's brilliant.
The show followed other, then modern, series like Star Trek: The Next Generation and Star Trek: Deep Space Nine. The former of which became the new film franchise after the conclusion of Star Trek: The Original Series' theatrical run.
Yet with the end of Voyager came the conclusion of The Next Generation's theatrical run. Voyager ended in 2001, while the last film to feature the cast of The Next Generation was Star Trek: Nemesis a year later. After Nemesis' failure, no Star Trek film was made for seven years.
And when it was brought back, it was a reboot of the Original Series. It's not a continuation of another plot like Deep Space Nine, Voyager or even Star Trek: Enterprise. While Enterprise and Deep Space Nine had a lot of meat left on their bones, Voyager really didn't.
So it made sense that the next film franchise wouldn't feature Voyager, one of their more popular franchises. The execs at Paramount clearly knew how popular it was. Series captain Kathryne Janeway, aka, Kate Mulgrew was brought in as a cameo in Nemesis, while Seven of Nine (Jeri Ryan) was originally written into the film with a meaty role.
The reason they were brought in or considered to be brought in is in part due to how popular they were at the time. Nemesis made no attempt to write anyone in from Enterprise, after all. So it wasn't about having tie-ins or cameos for the sake of it.
So clearly Paramount knew there were real possibilities here with the Voyager crew. Yet, a film was just not destined to work. How could it? The entire point of the show was to see the crew of the Voyager make it home. What else is left to tell with that concept?
The only way it can really work is if they brought the crew in under a new gimmick. Instead of the Voyager crew returning to the USS Voyager, maybe their part of the new Enterprise-E or on Deep Space Nine or on a completely new ship together.
Add in a few of the other characters from the franchise around this time and you got yourself an idea that could've worked. Yet, something so far away from the original premise doesn't really get to be seen as a continuation of the original story.
The Next Generation and Original Series didn't have a truly specific concept other than "Star Trek" and later "More Star Trek", so they worked better as films as their plots were pretty self-contained and translated pretty well to the big screen. Voyager and Deep Space Nine really didn't work as film concepts. Not as a whole.
So it makes sense why Voyager or DS9 were never really considered for the film treatment.