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.