The Time Travel Problem In Avengers: Endgame 1

At the end of Avengers: Infinity War, Thanos uses the Stones to cause 50% of living beings throughout the universe to dissolve into dust. For convenience, let us call this mass dissolution the "Vanishment"(V), let us call years after V "AV" and let us call events immediately before V "just before V."

In Avengers: Endgame (I might not have all of these events in exactly the right order):

five years elapse so we get to 5 AV;
surviving superheroes find Thanos on another planet and Thor kills Thanos;
Ant Man, who had not dissolved but had been trapped in the quantum realm for five objective years but five subjective hours (?), returns to the macrocosm;
he suggests -

superhero teams travel to times before V when it would be possible for each team to extract one of the Stones and bring them to the present which is now some time after 5 AV, say 6 AV;
use the Stones to restore all the people who had been dissolved but do this in 6 AV;
return each Stone to the moment from which it had been extracted.

Thus, the past would not be changed: the history of each Stone would be uninterrupted and the six years between V and 6 AV would not be affected.

What is wrong with this plan?