What I don't like about the Voyager finale is that Janeway essentially changes the timeline for selfish reasons, to save a few people she loves -as far as I can tell, no thoughts for the greater good of humanity involved-, and gets her way. Yes, adm. Janeway sacrifices herself, so in that sense she is not selfish perhaps, but only in the knowledge that a happier version of her will exist in the changed timeline. Tough luck for Carey, I suppose. He only died 4 weeks before but I guess he wasn't important enough for her to go back in time just one month further than those 26 years.
More in general, Janeway rarely gets to face the consequences of her actions, and even in those cases she often 'wins'. To a certain extent that's logical given their situation, given she's the top dog in the series - no superiors to correct her- , but still. She never had to pay the consequences for going too far with Lessing in Equinox for example, the way Sisko had when Starfleet took him off the Eddington case because he went too far. At least, we never saw it. When Chakotay tried to confront her, he got relieved of duty.
Granted, probably humanity is better off with the Borg hub destroyed and with future technology at their disposal. But it's still meddling with the timeline for personal advantage.
I mean, if this kind of time travel is OK, there's really no reason why Admiral Janeway (or someone else) couldn't go back in time to supply mid 22nd century Starfleet with some 24th century weaponry and make the Earth-Romulan have a more favourable outcome, with fewer Starfleet losses. But of course she won't because there were no close friends, so probably she would go hypocrite in this case, starting to lecture people about the 'temporal prime directive'.
That said, to be fair, Admiral Janeway isn't Captain Janeway who might invoke the Temporal Prime Directive, she's grown into a different person because of her experiences. Still, captain Janeway goes along with Adm. Janeway's plan.