With wind and solar we are capturing leftover energy from the sun's fusion; the internal amount of storage is not relevant.

With fossil fuels, we are simply using the stored energy from past fusion.

It's likely that we will start creating synthetic fuels from the electricity that comes from wind and solar, if you want a dense storage mechanism for keeping fuel close by for mobile applications or isolated sites.

There's nothing magical about nuclear, it's just a heat source. Unfortunately it's difficult to transmit heat long distances.