We don't build nukes because of cost. Anything else is propaganda.
We know how to design safe nuclear reactors. We just can't build them cost-effectively, because there is always some subsubsubsubcontractor that doesn't bother doing things by the book. Then an inspector notices that something is wrong and orders it dismantled and rebuilt. And this will be iterated until everyone manages to do the right thing at the same time.
It’s a space where you can’t cut corners.
- major accidents will be very rare (if any),
- industrial breeding will become possible (in order not to be dependent on uranium reserves or suppliers),
- nuclear power was the only option (at the time there were no industrial way to exploit renewable energy)
- terrorists, war and suicidal operators were not factors,
- dumping nuclear waste in various places (even in the sea) is adequate
All this is now way more difficult to believe.
Which is all to say -- it is not clearly and obviously correct to say that nuclear generation is cost prohibitive, and repeating it as if it were is a signal of bad faith.
(I still think it won't compete with solar+batteries. It still needs valves, turbines, and moving generators. Those things used to be considered cheap, but are becoming incapable of competing nowadays.)