I would think all the incidents with fracking have shown rock not to be as impermeable as one would expect or want. Doing this and not causing huge issues seems very hard to me. And also very situational, which is a big problem pumped hydro has.

Pumped hydro works really well and is just about as efficient as we can realistically do, but you need to have the right circumstances. Like a biggish elevation difference, a place to store enough water at the top and bottom for it to be worth while and a connection in between to pump through and take out the energy in the other direction. Plus close enough to a place that needs the power not to be killed by transport losses.

This thing seems to require the perfect conditions as well, which may prove even harder to find compared to places for pumped hydro.