I think that Bethesda can't help but notice things like "Fallout 4 is not the Fallout fans fell in love with", or "Fallout 4's factions all suck", or "Let's rank the Fallout games, Best to Worst" (an article in which Fallout 4 finishes last) on major video game blogs and realize that there are things they could or should have done better in Fallout 4.
Even if they can point to sales and conclude that someone (a lot of someones, even) really liked Fallout 4 they have to realize that there's some part of their potential audience that they could do a better job appealing to and sell even more copies.
They're not going to put on hairshirts and flog themselves with whips in order to atone for their sinfulness in crafting Fallout 4 the way they did, but there are bound to be a lot of entries on the "things we should do better" and "mistakes we can learn from" lists when it comes to making their next game.
It's simply not reasonable to look at the reaction to a particular work and conclude that it's all good or it's all bad. The sensible thing to do is to look at what you've learned, what you should do more of, what you should do less of, what things appealed to which parts of your audience, and which things repulsed which parts of your audience. It definitely seems that they have more to learn from the reaction to Fo4 than they did from the reactions to previous games, as the criticism of Fallout 4 was quite a bit louder than that of Oblivion, Fo3, and Skyrim.