I'm forgetting nothing. Q is a cheat. The Q move Trek from sci-fi into fantasy.
Don't like the gravitational constant of the universe? <snap>
Want someone back from the dead? <snap>
What's to stop someone from having Q undo all the damage the Borg did in Destiny? Why is Janeway worth saving but 60 billion others are not?
Well Beyer definitely did not make it a "Snap" to bring her back. And If you read carefully, you will see the undercurrent of destiny that is guiding even the Q continuum, so the Q do not and should not just arbitrarily change things because the fabric of the multiverse will unraveling if they do. It was not just Janeway coming back for the heck of it, she had to be there, she had to "die" and she had to come back. It need to be her on that bridge with Eden and the Q at the end. No one else could have talked Q down from not letting Junior go with Eden. It was a very metaphysical and epic return. It makes for larger than life stories, the kind Trek has been doing for years.
Also, the greater good is served by the events of Destiny. Beyer does a great job of explaining that the events have happened for a reason. If Janeway does not disrupt the Borg in Endgame, then they do not come for the AQ sooner than they had planned and the Caeliar, the Titan and all the the pieces would not have been in the exact right place at the right time to stop the Borg and the Borg would have taken over the galaxy. So 60 Billion die, but the galaxy is free of slavery forever. High price yes, but better than the alternative. Also if Janeway had been "alive", Voyager would have never gone back into the Delta Quad with Eden as captain and the very person that was need to stop Omega would not have been in the right place with Junior to seal it forever. Destiny, it's a beautiful thing.