In the Alpha Quadrant, the decision would've never have been Janeway's to begin with. In the Delta Quadrant, the lives of 140 other people likely depended on Janeway having the best advisers possible. Which was Tuvok and Neelix as separate people.
Tuvok and Neelix died, but Janeway had a backdoor to retrieve them. She owed it to her crew to do so. But doing so also wrongs Tuvix in the process.