Probably the most resounding criticism for Skyrim was the quality of it's writing and how most the adventures and quests you had didn't change much of anything, the people of Skyrim pretty much went about their business as if in a vacuum, no matter if the dragons were vanquished, the civil war had been resolved, or the emperor had been assassinated, Common comment was the game was miles wide, but only 6 inches deep. That had to sting at BGS.
For Fallout 4 it sounds from the voice actor interviews drama is being played up, and although not said directly how, both Todd and Pete have stressed that character development and story is an area they are actively expanding on in their most recent interviews. Obviously they are trying to improve, based on feedback. And while we can't be certain of it, the increase in the amount of time between games would suggest they are trying to deliver a game that has fewer engine issues. Let's hope they succeed on all fronts.