My argument is that they did really well with a moderate amount of resources. Economical. OP is making a similar point.
I think it's possible make a good game using only prefabs, sure. Depends what it is and what it's trying to do. Likely? No. Is ER an example of only using prefabs? Not at all. Did they reuse a lot of assets? Definitely. It's gigantic in scope though, and has a lot going for it despite the reputation, and even that repetition is managed very well in my opinion, is my point.
Why does it feel like the context and nuance of this is being thrown out to say, what, any repetition is bad? I did not say any asset reuse is good. I said it can be done well, and it is here. Don't take my point out of context and stretch it make it seem rediculous.