Star Trek: Voyager succeeded because it redid what the Original Series started.
The original Star Trek series featured a single ship and crew venturing around the galaxy looking for new life, cultures, and technology to learn about. Along the way, they also had to fight some baddies and teach some lessons but it was a show that firmly established an entirely new universe of aliens and concepts.
And while some of the Star Trek shows that followed it also explored new concepts and aliens, they mostly just went off of what was already established. Except for one show, Star Trek: Voyager. Voyager still leaned on all the same elements of adventuring and alien encounters that the rest of the series have done, but not to the same degree. At least not when we’re talking about already-established concepts and aliens.
Voyager did something that really only the Original Series did, which was create an entire show around whole new concepts. Granted, Voyager did still interact with creatures like the Romulans and the like, but at least 80% of their show featured aliens and technology not seen in prior shows.
And it’s one of the reasons that it works so well today.
Star Trek: Voyager continued the adventuring better than any other series.
When you think about Voyager, you rarely consider themselves in the same vein as the original series, but you really should change that mindset. The original Star Trek featured James Kirk and company going on a multi-year journey through space, where they’d often be by themselves and without help. Granted, unlike the crew of the Voyager, the crew of the original Enterprise agreed to this.
They were willing to go off into the unknown and explore. Voyager didn’t agree, but they still went off into the unknown to explore. They still met countless new species, discovered new civilizations and technologies, and dealt with heavy issues that had a larger message for the overall audience.
It’s truly the one show that matched the most to what Gene Roddenberry had in mind for Star Trek.