It's not that it can't be done on a technical level, it's that it can't be done on a social level.
Pumped (hydro) storage requires MASSIVE areas, all sorts of approvals, and often resettling people. This works fine in China where the government can just do whatever, but in places like California, we can't even approve new resevoirs for drinking/farming water, much less energy storage.
Can that change? Certainly. Is it likely to? Doubtful.
I'm not talking about pumped hydro. Batteries have largely rendered that obsolete. And batteries are scaling like gangbusters.
Realize that even in a fully nuclear powered world, huge amounts of batteries are needed. Replacing every ground vehicle in the US with a 70 kWh BEV would require enough batteries to store about 40 hours of the current average US grid power. So the scaling is needed regardless of the post-fossil energy source.
A longer term storage mode is also needed to deal with seasonal storage and covering rare Dunkelflauten as batteries are not suitable for that. Fortunately there are multiple ways that could be handled, so it's a question of which is best.
Pumped (hydro) storage requires MASSIVE areas, all sorts of approvals, and often resettling people. This works fine in China where the government can just do whatever, but in places like California, we can't even approve new resevoirs for drinking/farming water, much less energy storage.
Can that change? Certainly. Is it likely to? Doubtful.