Sure, if we could snap our fingers and have a bunch of nuclear plants it would make sense. But the tech is all ancient, and the regulatory structure is oppressive. It will take decades to build out the amount of nuclear capacity we need and cost inordinate amounts of money, and we've already passed the tipping point where renewables are the better choice.
Just as an example, it took us 14 years to build a single reactor in the Vogtle plant costing over $30 billion dollars. We'd need massive reforms to the regulations and supply chain for building reactors to bring those numbers down and that just won't happen fast enough.
Even China, who is the world leader in nuclear power these days is slowing down building of new reactors in favor of renewables, and they do not have the regulations and supply issues we have in the USA.
I wouldn't call it defeatist, nuclear should never be more than a stopgap to 100% renewables. if anything, it's awesome that we've gotten far enough with renewables that switching to them entirely is now a viable proposition. It sucks that we spent so much time dependent on fossil fuels when we could've been using nuclear, but the past is the past and the future is bright.
I will say, small modular reactors might have a place in the energy mix. They would be fantastic for more isolated grids where stability is difficult to achieve with 100% renewable energy. Think small island nations or remote areas. Also would be good for emergency and disaster recovery scenarios. We (as in the USA) also already have the supply chain to build them somewhat efficiently since we use them on our aircraft carriers. Just needs some tweaking to work well on land and for the regulations to loosen up to make it economically feasible.