Not discussing with the falling cost of solar and wind - but recently I have read a good argument about why nuclear is expensive:

""" Excessive concern about low levels of radiation led to a regulatory standard known as ALARA: As Low As Reasonably Achievable. What defines “reasonable”? It is an ever-tightening standard. As long as the costs of nuclear plant construction and operation are in the ballpark of other modes of power, then they are reasonable.

This might seem like a sensible approach, until you realize that it eliminates, by definition, any chance for nuclear power to be cheaper than its competition. """

https://rootsofprogress.org/devanney-on-the-nuclear-flop