Kate Mulgrew played Captain Kathryn Janeway for seven seasons on Star Trek: Voyager and has since played her (and Admiral Janeway) for two more seasons on Star Trek: Prodigy. So it's blatantly clear that she knows this character inside and out. The character wasn't her idea, but she built Kathryn Janeway from the ground up. So when she says a return to a live-action form of the character would have to be "so good," it's understandable.
Back in July, Mulgrew told Trekmovie that she was "entitled, I think, to tap into that sense of protectiveness of that character." She has a lot of respect for the character that she imbued, and it's no wonder that she would want to protect that Janeway's legacy as well as her own.
When sites create lists of the best captains of Star Trek or their favorite captains, Janeway is always high on the list, which should come as no surprise to fans of Voyager. Here was a captain that was placed in a virtually impossible situation—getting her crew back home safely even though they were 70,000 light years away—and didn't fold up like a cheap suit.
There were so many ways Mulgrew could have played this character, but the strength she portrayed as a captain with a heavy sense of duty on her shoulders was exemplary. It was something no other captain had faced or has since. And Mulgrew injected just the right amount of confidence without any hubris.
Janeway didn't know if she could get her crew home, but she was determined to keep trying. Voyager faced overwhelming odds, and, at times, there was doubt the crew would make it home. After all, at that time, we didn't know how the series would wrap up. But Janeway was the backbone of her crew, and they never saw her fall apart or doubt they would make it home.
What Mulgrew created was a force. Millions of viewers then and today can look at this captain and feel like any goal can be achieved if they don't give up. Giving up wasn't in her vocabulary so when Mulgrew says she's entitled to be protective of the character, we have no reason to question the veracity of her statement. After Captain Kathryn Janeway was created on paper, Mulgrew gave her life and a memorable one at that.