Even if every bit of regulation was scrapped and uranium was free, there are still significant costs to steam turbine based thermal plants plus the reactor itself that can't be hand waved away. As PV costs and now grid-scale storage keep dropping rapidly, the economics of a nuclear plant that takes 5-10 years to get running at full capacity (in the very optimistic case) and even longer to break even look increasingly questionable.

PV solar + batteries is a dead simple, solid state design that's easily scalable without huge up front capital requirements. We're not at the point yet where nuclear doesn't pencil out anywhere, but with current trends it's getting closer by the year.

I wish we built more nuclear 20-30 years ago when the competition was coal and gas but unfortunately we didn't and now the equation has changed. Shutting down existing reactors that are still viable is a bad move to be clear, but new plants are becoming increasingly hard to justify economically.

It's unclear to me exactly why building big projects is so expensive, but it's not just nuclear. In the US, subway expansion, high speed rail, and bridges are also ridiculously expensive. Whatever is causing the runaway costs and schedules doesn't appear to be related to it being a fission plant.

I would love it if somebody who has recently built something like a fission plant could give us a report as to exactly what happened that caused this.

I think you're off by an order of magnitude there. Intensity should be somewhere between 150 to 300 watts per sq meter per 24 hours. At 200 watts per sq meter that works out to 5 sq km. Estimating 50% panel efficiency that's 10 sq km.

To hit 100 sq km at 50% panel efficiency would mean averaging 20 watts per sq meter (obviously wrong). Even assuming a paltry 10% panel efficiency would only get you to 100 watts per sq meter.