Inefficient storage is pointless. If it ends up being cheaper to throw the surplus away and then later run a fossil fuel generator, people will do that.
Time-shifted heating has long been a thing in the UK; "Economy 7" electricity is cheaper at night, used in conjunction with oil-filled storage heaters.
"Pump water up hill" requires a suitable hill. There are not nearly as many of these as you think, and flooding them is environmental damage of its own.
There's also a difference between using a substance re-usably for energy storage, versus extracting a non-renewable resource and burning it.
Grid-scale batteries are key to getting to a situation where most energy is renewable. The other tech that might work here is the molten salt battery, but that's harder to handle and doesn't scale down well.