Perhaps the combination of ideas is more important for Bethesda's fanbase than the quality of implementation of each idea? Imagine what'd happen if someone were to copy what Bethesda did only do it way better. Better shooting elements, better RPG elements, better overworld for exploration, better crafting systems, better dialogue, deeper character relationships etc. How many Bethesda fans do you think would jump ship? Hell, FNV put a dent in Bethesda. Some of their fans wizened up after they saw better quality and are now asking for more. They've seen that they don't have to settle for the shit Bethesda shovels them and want more. But FNV still suffered from a lot of problems being held back by Bethesda and their engine. Imagine someone else with a different engine pulling an even better FNV-esque game?
I honestly think that's the only reason a lot of Bethesda fans are even sticking around with Bethesda. They ain't got anyone else to move on to. Sure, if they want straight up shooting then they could go to COD or whatever. If they want a romance sim then there are tons of them out there. But if they want the kind of gameplay Bethesda offers then what options do they have? I believe that if they were given a proper option that is just somewhat better than Bethesda in each individual element then they'd see a massive drop-off from their fanbase.