The point is this: renewables are getting cheaper faster. Batteries are getting even cheaper even faster. Batteries can support the grid. The demand for batteries to support the grid is going up exponentially whether the renewables market growth speeds up or slows down, because the grid is always short of storage, because energy generation investment always leads energy storage investment, irrespective of energy source. But because storage production can now grow even faster than generation production (this has never been the case before, it was always too expensive) storage can tap into pent-up demand that has been building up over decades. You are absolutely correct that batteries were not scalable before: they are only just crossing the scalability curve.