I had the same thought recently, that if a new power source was created that was like, a perpetual superheated cube or something with no input costs, it still might actually be beaten by solar + batteries. If not right now, then in just a few years.

Since you'd still end up having to build a gigantic heat exchange setup with steam turbines, pipes/ducts/pumps, generators, valves, gauges, vents, maybe even a cooling tower, etc. Plus a labyrinth of catwalks, ladders, access tunnels for workers in hard hats servicing/inspecting/replacing stuff who are on-site 24/7 and exposed to non-trivial occupational hazards dealing with superheated liquids at high pressure every day.

The entire concept of a steam turbine is just fundamentally a big hassle compared to an inexpensive solid state slab + batteries that are modular and basically plug-and-play by comparison.