A single solar installation on the scale required to replace the output of one nuclear plant also takes many years to come online. You're not wrong that new nuclear projects take a long time to start producing, longer than any other power solution, but new solar projects of that magnitude don't pop up overnight. There's still bureaucracy, funding, land acquisition (and boy do you need a lot of land for enough solar to offset even one nuclear plant), construction, power grid connections, and sourcing/manufacturing the actual panels.

The median reactor in the US produces 1-2GW. Most nuclear installations have multiple reactors, so capacity is a multiple of that. 1GW of solar generation requires literally millions of solar panels and thousands of acres of land, and still needs the transformers and distribution infrastructure. And that doesn't include any storage capability.

This is a contrived example. You're making it sound like solar is power available now. It simply isn't, on any scale like that. If it takes a decade to bring 1GW of solar online and two decades to bring 1GW of nuclear online, it's not as clear-cut.

Nuclear could be done a lot more quickly than it is and still be safe. Not as fast as solar, but it's not like it's an order of magnitude.

Build nuke and solar then. The more the merrier.