Energy storage is a simple matter of civil engineering: a big job to construct enough, but requiring no new technology.
We are not building it now because it would be stupid to build storage there is no renewable capacity to charge up from. Money is overwhelmingly better spent today on renewable generating capacity.
By the time we need to build storage, it will be much cheaper than if built today.
Solar power is very cheap, but a complete 24/7 solution requires batteries. Those are much more expensive than the panels. A better battery is all we need. Panels are good enough already.
Large-scale storage will be very cheap, on par with panels. It really is just civil engineering. Any competent civil engineer can sketch a practical, cheap storage system using only century-old tech.
Hand-wringing over utility-scale storage amounts to concern trolling.
Also: why must the highly variable renewables share the grid with highly variable demand, use them to make hydrogen (only when the sun is shining/wind is blowing), feed that into a totally separate power plant, simple to manage - if renewables really get cheap who cares if it's inefficient.
https://en.wikipedia.org/wiki/Compressed-air_energy_storage
https://en.wikipedia.org/wiki/Metal%E2%80%93air_electrochemi...
For long duration storage: hydrogen, ammonia.