LOL, you know I hear this all the time, I really liked the voice acting in FO4 why did folks hate it so much? ( I played the male protagonist)
I think people are used to generating their own "headcanon" for each Fallout protagonist (on each playthrough) due to the elements of moral ambiguity present in each game, and it becomes more difficult to do when they always sound the same, and in addition to that are given a very specific backstory leading up to the events of the game (military father / lawyer mother of son whose spouse gets killed and kid gets stolen). Dialogue options were more "railroaded" as a result of this compared to the previous entries in the series; FO3 for instance very often had more than 4 things you could say as a response and it usually wasn't the case that 2-3 of them were just different ways of saying "yes".