Bringing a new nuclear plant online safely takes decades, and decomissioning one takes even longer if you include its nuclear waste. Nuclear is not an agile solution. This won't change in the near future, or perhaps not at all until "nuclear" becomes synonymous with fusion, not fission like today.
Nuclear is also an extraordinarily expensive technology which limits its uptake to only the more afluent of nations. Furthermore it is highly regulated for very good reason, and the politics of nuclear power again limit its global uptake. If we have to rely on nuclear to get us out of the CO2 mess then we are doomed, because it's a global problem.
But we don't have to rely on nuclear, we can just stop burning fossil fuels, and stop using so much energy overall. It would require an immense social adjustment to achieve this, but it has no roadblocks other than making people care enough to do it.
The main showstopper to controlling our current destruction of the planet is profit-seeking capitalism, because it would die in the absence of perpetual growth. Nobody has yet come up with a solution for dealing with that.