How would the Borg do that if the hub, uni-matrix complex and billions upon billions of Borg were destroyed?
I would think it would take the Borg many years to recover, much like Federation has to recover after the Dominion war. Janeway didn't make it worse, she leveled the playing field.
What I gave was one scenario, there are limitless problems with Janeway's actions.
here's another scenario. Perhaps another unknown threat develops in the delta quadrant. That threat, would've been destroyed, or at least held back or in check by the Borg. Due to Janeway's actions... the borg are to weak to defend against the new threat, which them moves on to attack/claim the alpha quadrant where the federation lies...
(Here's another far out scenario. Perhaps Chakotay and Seven have a child that turns out to be the "Hitler" of the federation. That child was never born had Admiral Janeway not altered the timeline.... like I said, limitless problems could occur)
Fact is, Janeway had no idea of knowing what future problems could arise from her altering the timeline, which she did only for HER SELFISH reasoning.
This could have been avoided had they painted a different picture of the Federation in the early portion of the finale. Had they made it look like the Federation was in serious trouble and in serious decline, then going back and hitting the Borg early makes sense. BUT THAT WASN'T IN THE EPISODE.
I don't see how you can so easily write off that what Admiral Janeway did would not have any future consequences.