The US at least already has enough nuclear to handle base loads when solar and wind are unavailable. Nukes in some contexts are needed, but I believe we have 30% or so nukes in the US. Diverting resources to new nukes is a waste when we could be making carbon fuels unprofitable soon by investing in solar and wind.
But are they in the right places? There’s always loss in power transmission, so you can’t use reactors that are in, say, Illinois, to make up for grid deficits in Alabama (or, not directly). And Texas, being a special snowflake, isn’t tied into the national grid, so they always need their own systems.