This isn't a game of Top Trumps where you need to find any one stat that's higher than your opponents to declare victory.
Nuclear has to be better than wind and solar and hydro and batteries and everything else (demand response, better insulation, undersea grid connectors etc.) all working together across a wide range of metrics to find a place in a modern grid.
It is failing at this. The alternatives are cheaper, better, greener, safer, quicker to build.
Narrowly focusing on one tiny aspect does not change this big picture reality.
The problem with what you're saying is that to supply peak power at all times could require building capacity in each method to supply full power, in case the others all fall to zero power. And even then, you hope that they don't all fall to zero, I guess.
If weather gets hot, the temperature of the incoming cooling water gets warmer, too. And having to operate within the limits of the maximum allowed temperature for the outgoing cooling water, the plant may have to regulate its power output, or maybe entirely pause operation.
The temperature limit is mostly a legal one: There is concern about the environmental effects of releasing warmer water to the water bodies. From an engineering point of view, the plant would probably be able to operate, and just release warmer water.