If we consider Sisko’s personal vendetta a bad thing that makes us question his authority to lead, I don’t understand how we excuse Janeway and the time travel stuff she pulled to get Voyager home–her actions had exponentially more butterfly effect consequences than Sisko could ever dream of.
It also fits with what we know about her. Janeway was always second guessing her decision to ultimately strand her crew in the Delta quadrant. She felt extremely guilty about all of the people on her ship that got killed through those 20 years (especially Seven of Nine) and wanted to do something about it.