People always forget that batteries also absorb power. Having a lot of renewables means there are energy spikes far exceeding what can be used in that moment. Without batteries, that energy is lost. Having batteries means that energy can be buffered and used later (e.g. in the evening). So they improve the capacity factor of existing installed renewables. Add domestic batteries, EV batteries, etc. to the mix and you also get the potential for demand shaping where you charge those when renewable energy production is spiking and prices are low. And of course even though that is currently not utilized on a large scale, all those EVs could technically provide energy back to the grid as well.

Another point is that batteries like this are not actually intended for long term storage. They are instead about stabilizing the grid and dealing with short term spikes and dips in supply and demand of energy. Unlike a coal or gas plant, a battery can respond in milliseconds and be very cost effective for that. Spinning up coal and gas plants is expensive and slow. And they cost money when they are not running.

And while that single coal plant was able to provide so-called baseload; it would only have been able to do so if it was up and running 24/7/365. And that wouldn't be true. They are very reliable but occasionally coal plants have to be down for maintenance, repairs, etc. and this can take quite some time (weeks/months). Same with nuclear plants. So, relying on that to not happen was never a good plan.

Long term storage is always assumed to be needed to compensate for a lack of this baseload. However, baseload is actually a fuzzy notion until you express it in gwh and gw. Hawaii seems to be in the process of proving this might be a lot less than some people seem to assume. At least I'm not aware of them having any long term storage. They'll probably add more battery and resilience to their grid over time in the form of more wind and solar generation and additional batteries. But if these people modeled this correctly and did their homework, this might actually be fine as is. We'll find over time I guess.