For nuclear to be viable globally, which is necessary to solve climate change, it would mean trusting other, far less developed and unstable countries to build and operate nuclear power plants. That is something that even the US, the USSR and Japan have all occasionally failed to do correctly with significant consequences. The UK has a ton of hot nuclear waste that is still improperly stored due political issues. I don't think there's political appetite for expanding the set of countries with access to fission.

Solar, wind, geothermal, biofuels etc. are imperfect, but it's hard to imagine a scenario where a mistake can make a significant chunk of the earth uninhabitable for hundreds of years.