So when humanity eventually runs out of fossil fuels and uranium ores, we're just going to go back to the pre-industrial era?

You can build an entirely solar/wind-powered storage and distribution center capable of putting out 1 GW of power 24/7 with modern PV panels, wind turbines, battery storage, hydrogen storage, etc. It's entirely feasible, and although costs for such a system are high (comparable to that of a 1 GW nuclear power plant), those costs are steadily falling and the long-terms costs are much lower as you don't need to acquire uranium fuel or store the hot waste.