The thing is we don't live in a fairy tale, we're limited in resources and time. We can't ditch both nuclear + fossil right now so we have to prioritize one over the other for the next xx years until we figure out a way of making renewables good enough, right now they're a good addition at best and a gimmick at worst. And it's not like renewables are a silver bullet either. If you ditch nuclear to import panels or wind mills from countries like China I'd like to see a full life cycle pollution/emission report