It’s super expensive and it takes forever to build—so much so that fossil fuel companies fund “libertarian” voices to use it as an attack on environmentalists because nuclear means decades of unabated fossil fuel sales. If you commit to solar or wind, you start cutting into their business within as little as months.

Not cost competitive with solar+batteries in many locales (less so the closer to the poles), and no learning curve, if anything a negative learning curve, nuclear never was more expensive than new nuclear.

And off course societal (and geopolitical) acceptance issues.

Its really, really, really expensive to build.

And people are (mostly irrationally) terrified of it, which matters in democracies.