That will still take at least 20 years.

"A society grows great when old men plant trees in whose shade they shall never sit." Long term investment into the future is a good thing.

I agree with that sentiment but do we have 20 years to spend waiting to stave off climate change?

I'm not saying to only build nuclear, but it'll certainly help us out down the line, and not building it is almost certainly far worse than the potential of it being slow to build.