One basic cost problem is that nuclear power plants are built as one-of-a-kind. If they were built in serial production, the costs could be brought down significantly. But this is all heavily related to the scaremongering and hysterical opposition to anything nuclear (serial production -> smaller sites -> more NIMYism...).

If everything was rosy in the renewables, then why not. But we don't have storage, we don't have high-capacity long-range (thousands of kms) energy network, most of the production capacity is in China ...

Both directions have its risks, I think a wise choice would be to pursue both to avoid putting all eggs into one basket.