What nonsense. I'm not denying power or energy density of nuclear is higher, I'm denying that this bare fact is relevant to any decision that we might make about using nuclear to power civilization.

And no, power and energy density do not determine cost, in general. They might if all else were equal, but all else is NOT equal. Renewable sources can omit entire categories of equipment that thermal power plants require, and have a much lower requirement on reliability (both because the individual units are smaller, and because the consequences of their catastrophic failure are vastly smaller.)

And no, nuclear's longevity and reliability do not pay for themselves. You're engaging in a bit of confrontation with economic reality there.

Pointing to nuclear reactions occurring in the Sun and pretending that justifies using nuclear on Earth is just completely absurd.