I feel as though you are simply picking the "worst" of GTA and the best of Fallout to justify your argument and kind of missing the overall picture.
The fact is that all games must re-use assets, it is in the nature of game making that limitations must be worked around. There is no point arguing this game re-uses that or this, all games do it, period. It is a matter of how creatively this is integrated into the game in a discreet way.
GTA is never obviously copy pasted, your examples about the shops could be argued that the similarities are there to be easily identified and familiar to players, as well as possibly the fact that these stores are franchises. Does every Macdonalds you walk into have it's own unique look to other Macdonalds restaurants?
I also think you are over stating the "interactivity" of the NPCs in fallout. Most you cannot engage in dialogue, they simply just say one line and move on. A few have names and are part of the story. The rest are completely as generic as pedestrians, Super Mutants, Raiders, do not act in any surprising way. And far an few between, as is appropriate for an apocalypse.
The point is the argument that somehow the way Fallout is makes it too taxing to have better graphics is completely flawed and comes out of a place of where? How well do you know about how this game was actually made. Have you see behind the curtain? Been to Bethesda studios? I find it very hard to believe the graphics are shitty because they have to be. Games on last generation (hardware more than 10 years old) have superior facial animation, animation in general, special effects, terrain etc etc. The truth is if Fallout was made exactly as it is by a studio like Rockstar, it would be just as interactive and 10x better to look at. The only argument that makes sense is that Rockstar is much bigger and well equipped, true. But that doesn't give a free pass to how the graphics stand as they are.