As for time, the majority of this 20-30 years estimate consists of inertia and bureaucracy. As a country, we've built far more complicated (Apollo Project) and high-risk (Manhattan Project) things in the past in a compressed time frame, we had no choice then because we've faced clear existential risks. Our inability to countenance all this today says more about us as a society, than it does about the do-ability (within say a decade) of the task at hand.
I guess I can agree with you, but only as pessimist, which is a darn shame really.
PV manufacturing is complex and expensive. Most of the cost of PV is in the manufacturing machinery, since the raw materials are cheap. Adding new manufacturing capacity takes time.
It may be that PV can be ramped up faster than nuclear, but some of the new nuclear designs (NuScale and Oklo) could be cranked out pretty fast also.
These aren't insurmountable problems, but they are pretty big. With solar, a person can stick it on their house. A grid-level installation can be built over time and starts paying for itself as soon as the things are plugged in.
Our current plans are targeting 2030 for massive carbon reductions, right? I don't see how starting a bunch of nuclear plants now really helps there. The most enthusiastic proponents of preventing global warming have always wanted to target 10-15 years out, so the energy isn't there for nuclear. Unfortunately. It would have been nice if we'd built a bunch of nuclear reactors 30 years ago.