You know what pumped storage hydro is? A battery. Unfortunately that is not an option everywhere and takes up a massive amount of space. The space portion is not a huge issue for grid energy storage for the most part but it can definitely limit where you can do it and its capacity.
As for the amount of lithium available, there is absolutely more than enough considering it is one of the most abundant materials on our planet. Not that we need to use lithium for grid energy storage. Lithium is very high density energy storage which you are correct that is not a high priority for grid energy storage.
Basically there is no one solution for grid energy storage. There are mechanical batteries, medium density chemical batteries, and even “depleted” EV batteries. We just need to apply what is right for each particular scenario.
I’m not disagreeing with you overall. But I figured more info and context is helpful.