It would've helped a ton but it's not like electricity generation is the only source of emissions. You can't run a car or a plane on nuclear power. You can technically run a cargo ship on nuclear power but that's also not gonna happen. Yet transport is the second largest source of emissions.

Batteries have only recently-ish gotten energy dense and cheap enough for electric cars to be competitive, completely different solutions are needed for long distance shipping by sea or air.

It's the same situation across many other sectors like agriculture, construction and waste management. Lots of things causing emissions that's not electricity generation.