Earlier quoted context omitted.
You have to pay off the initial construction costs. Throwing away half the energy you generate means that you're wasting the large up-front costs.
Right. If we build nuclear plants to fulfill peak energy demand (which coincides with a lack of energy production from solar) then there's not reason not to just run the nuclear plants 24/7 and skip building solar altogether. This is why nuclear power and intermittent sources end up being a dichotomy in practice. Solar does provide a good way to mitigate carbon emissions in the meantime, even if it's role in a fully…
How much would it cost to build nuclear power generation capacity to meet peak demand, vs. building a grid with renewables, long-term transmission and storage? The levelized cost of solar and wind power is way below that of nuclear power (and that difference will become much larger if you're only fully utilizing nuclear power during the daily peak demand), so the question is how much storage and transmission add for renewables.