I would gladly pay US$60 for Fallout 4, despite its flaws. But not everybody has to have a massive, handcrafted (i.e. labour intensive and hence costly) open world. It sort of goes back to the complaint that every AAA game has some bog standard gameplay elements. Those bog standard elements cost money, while the return of investment (i.e. gameplay hook to players) may be minimial.
If your sequel has to be bigger and better, then the easiest way is to make MORE of everything, not something different. Nowadays AAA developers are getting burned because 2x bigger in everything doesn’t necessarily translate into 2x gross or even net profit.
For example, I’m completely ok with Ubisoft’s iterative approach to making Assassin’s Creed. Every new game every year has something different, but not necessarily bigger than the last one. It doesn’t have to be, as long as there are new and interesting things happening. This year it is Paris, next year London etc. And then they just dropped the iteration and opted for a big bang in Origin. It is still an open question whether Origin will be as big a hit as the investment suggested though.