Even if the current solutions are inadequate, the same was true for PV 20 years ago, it just needed investment in R&D. Investment in R&D of grid storage is at the highest in history, and growing.
The real question is at what relative cost level it turns into an S-curve. Right now renewables are mostly cheaper than non renewables and transitioning to a lot cheaper. A lot might turn into one or more orders of magnitude. Where does it stop? Two? Three?
What's the ultimate cost of a mwh of power? It's probably a lot lower than what people currently pay. Renewables have a bit of upfront cost but the marginal cost of using the equipment is close to zero.
Lower cost of energy opens up new use cases and drives the market up. Basically it causes people to electrify more things. Even things that we currently think of as too costly. As those things get electrified, they get cheaper. And there are people that make the investment and benefit and people that don't and get pushed out of the market.
Current grid storage technology is a few breakthroughs away, we just don't know when it will happen but given the amount poured into R&D for it, the willingness of governments, and technological hurdles that are orders of magnitude lower than fusion I don't see why we can't expect it to become reality in the next 10 years.
As I said, it's lagging the curve of solar adoption, China has invested a lot in solar for their own power needs as an oil-poor country, their options are renewables and uranium, with the EV industry booming in China, solar being widely adopted, I don't see why they couldn't be at the forefront of grid storage as well in a few years (5-10).