Gigawatt scale solar installations can and have been built in under 2 years in the US.

Your link shows that China & Japan can build quickly now, and that the US and the UK could build quickly in the past.

Also keep in mind that the limited amount of data for US/UK plants are for long planned expansions. Vogtle was built to accomodate 4 reactors from the start. So Vogtle 3 & 4 should have taken considerably less time than average.

But let's be generous and say that a greenfield project takes less time to construct than Vogtle, or 10 years. Do you think planning & approvals can be done in less than 10 years?

Even the touted "small modular reactor" projects take over a decade. For example, the INL small reactor project started in 2013, kept getting delayed until it had a start date of 2030, and then was cancelled a few months ago.

And meeting demand with nuclear would require around ~200 full size reactors. 20 years to build 200 reactors sounds extremely optimistic to me.

If you are a capitalist looking for a return on investment, the best time to build a nuclear power plant is probably going to be "whenever we run out of places to put solar panels and wind farms".