So after 10-20 years of construction and cost overruns and 10-20 years of operating at a loss you start making money.
And that's assuming electricity rates don't drop in that time. Which they are as renewables get deployed more and more because they don't go 100% over budget in time and money.
If we get started building nuclear power plants now, how much will storage and transmission tech improve before they're even completed, let alone profitable?