Battery power could entirely satisfy the need with the right quantity, it just hasn’t scaled up yet.
The typical coal plant takes up 0.7 acres per megawatt of power generation. 0.7 acres of sodium-ion batteries can store 10-100 MWh of energy.
10MWh of energy is 36 seconds worth of output from a smallish 1GW power plant. Battery storage is a huge way off viable for anything other than smoothing out daily cycles of wind and solar.
A 1GW plant takes up 832 acres, which would be 12 hours of power with 10MW of storage per 0.7 acres, or 120 hours with a high density 100MW configuration.
Smoothing out the daily cycles is exactly what we’re discussing: absorbing the excess during peak and using it to power through the troughs.
No the discussion is on making a 100% renewable energy stable grid. There are three levels that need to be managed for this, the daily cycles, (mostly of solar being unavailable at night), the yearly cycle of solar giving more energy in the summer and wind more in the winter (generally) and the meso scale of weather.
The first can be probably sorted with storage with work. The second mostly balances out if you have a mix of solar and wind luckily, but the third does not have a solution at the moment, there isnt a feasilble way of managing a 10 day strech of dull still days in winter without firing up a large amount of gas peaker plants. Even with your proposed 800 acres of high density storage (of a currently not fully proven type in Na batteries) per small powerplant, a vast amount, would give 5 days worth of storage which wouldnt be enough to cover the once a year, once a decade etc poor weather condiditons.