Baseload is simply the lowest wattage your grid demands in a time period. Solar and wind have not made it irrelevant at all. All of the demand from data centers very much assumes constant reliable power which is in fact a perfect match for nuclear.
Nuclear power’s problem is that neither its spread between CAPEX and OPEX, nor its operational profile fits them.
We also have electricity futures. Again with the problem that their cost is far far below what new built nuclear power requires.
Here’s some reading on electricity futures:
And even if they sign a PPA the renewable arbitrage they could do exerts large downward pressure on the price they are willing to pay.
Which is to say, they would want to sign a contract saying ”deliver cheap reliable electricity when renewables and storage doesn’t do it”.
And now you are trying to fit an extremely CAPEX heavy square into a round OPEX sized firming hole.
Thats what OP means by baseload generation being irrelevant.