This is a nonsense argument. How does the energy density of renewables prevent them from providing all the energy we need? Show us the quantitative argument (spoiler: you will not be able to do so.)
It’s not about total capacity they can provide, it’s how quickly and efficiently they can provide a unit of energy capacity, and how much carbon those materials themselves produce during manufacturing. Nuclear is, across the board, more efficient. Solar simply isn’t efficient enough, strictly speaking in terms of output per unit of input, to generate the energy we will need to reverse climate change and reduce current emissions enough.
Carbon produced during manufacturing is a bad metric right now. If producing a MW of levelized capacity for solar (say) causes emission of twice the CO2 of a MW of nuclear, but displaces much more CO2 of fossil emission per $ invested than nuclear, then going with solar displaces more CO2 than going with nuclear, for a given investment budget.
Also, the CO2 emission is a function of the level of fossil fuel use remaining in the rest of the economy. Transporting materials to the site depends on whether those vehicles are burning fossil fuels or not, for example. The focus on current CO2 from manufacturing is implicitly assuming that we will always need fossil fuels to build these things, that the processes and materials can never be performed/made with non-fossil inputs. With that assumption, we're doomed, so the difference is irrelevant anyway.
