In the past fracked gas and unpriced carbon externalities have been the big factors for nuclear cost disadvantages, starting roughly about now (and already in some places) renewables will be doing to gas what gas has done to nuclear and take nuclear (and coal) out at the same time as a byproduct.
A carbon tax would give a short term boost to existing nuclear over gas, which is one of the many reasons it's a good idea, but it also accelerates renewable adoption and price declines which already render new build nuclear ridiculous in economic terms.
Fracking changed the economics of all energy production, not just nuclear. The economic case against nuclear is that it can potentially wipe out everyone in a 50 mile radius. The cost of a nuclear power plant is therefore proportional to the surrounding real estate value.
Meanwhile nuclear plants are being built at a good pace throughout the world.
A lot of the “anti renewable” people I know are some of the biggest proponents of nuclear. It’s strangely a popular position among America’s “right”.