This just isn't correct. There are dozens of pilot projects for novel grid storage systems being built right now all around the world, and existing battery based grid storage like Tesla's megapack have multiple installations already in use, and dozens more planned this year. Pumped hydro alone is already in the hundreds of GW range.
The reason grid storage hasn't been built is because batteries were too expensive, but more importantly, grid storage was never needed. It takes 5-10 years for new tech to see widespread deployments, and it's only been a few years that grid storage had been getting this investment.
And as I said, we have hundreds of 100MWh+ battery plants, and hundreds of GWh of pumped hydro. The idea that they haven't been deployed at scale is just wrong.
The reason grid storage hasn't been built is because batteries were too expensive, but more importantly, grid storage was never needed. It takes 5-10 years for new tech to see widespread deployments, and it's only been a few years that grid storage had been getting this investment.