The point here is that each $10B spent on new generating capacity displaces some amount of coal generation. If you spend your $10B building nukes, it displaces A million tons / year of coal output, if you spend $10B building renewables, it instead displaces B million tons.
And B is much larger than A, because a GW of solar + storage is much cheaper than a GW of nuke.
The corollary is that each $ diverted from renewables to nukes is not just harmful, but brings climate disaster nearer. Best, of course, would be to stop diverting money to fossils, but all we can do about that is build out renewables + storage as fast as we can. Renewables will be running at 100% at all times, and each kWh produced displaces a kWh of fossil generation.
Displaced fossil generation in most markets is methane gas, because methane gas is cheaper and therefore preferred. But! anywhere coal is being used at all, they will prefer to cut coal output because cutting coal saves more money than cutting gas.
A particularly good example is Germany, where they cannot get enough natural gas to meet their needs, and are burning coal like nobody's business. Every last kWh of renewables + storage that can be put on the German grid, provided it is steady-enough output, displaces exactly that much coal.
The cost of storage is plummeting even faster than of solar or wind ever did, so there is some short-term sense in delaying storage build-out until it is cheaper, so you can buy more of it. But in the big picture, building out storage at any price is much, much better than waiting.