Grid scale storage is actively being worked on.

Chemical batteries, like rechargeable lithium ion batteries, are a big part of it. Sodium ion batteries and iron air batteries are coming up, as well.

Somewhat related are rechargeable fuel cells and flow batteries, that similarly store chemical energy that can support two-way charge/discharge cycles.

Gravity storage, like pumping water up into a reservoir and then using it to drive turbines on the way down, or elaborate elevator shaft type systems, can store some energy but require lots of land and material, or require very specific geographic features not commonly found.

Kinetic energy storage, turning lots of heavy flywheels and then recapturing that momentum to produce electricity when needed, is also on the grid (and kinda mimics the rotational inertia of the turbines traditionally synced across the grid).

Some other storage technologies include capacitors, pressurized gas containers, and thermal heat storage with molten salt that can be used to make steam to drive turbines on demand.

But all of these solutions are difficult to scale up to the point where they make a significant difference in addressing the mismatch between supply and demand at different times of day. We gotta do all of it, and right now the most cost effective solution is chemical batteries, so that's been growing at an exponential rate.

Like, there is a huge focus on inventing and implementing exactly this. I have seen many technical science/engineering articles about the different approaches to make it work. Because it would be amazingly useful. But the solution has generally not been found yet.

Reality bites. Some stuff is just not possible to make economically. You can't just say "economics of scale" like it is a magic incantation.