I've read somewhere that the baseload thing is a myth and that solar+wind doesnt really need baseload power at all. Is this true?
I've also read that battery costs are already low enough for energy storage to not be a financial hurdle in full decarbonization. So if this is true, why do we even need nuclear?
The battery thing isn't true. Lithium ion batteries are cheaper than ever before, but the problem is there literally isn't enough lithium in the ground to run the world on wind and solar. Perhaps this would be possible with other battery technologies that haven't been developed yet, but it isn't true now. New technologies would be needed to completely decarbonize without nuclear. (Yes, I know pumped storage exists. It's inefficient and requires specific geographic features.)