> Doing something smaller, but more often, is how you get good at most things!

And yet, for most things, we see the opposite trend. We build big factories, big ships, big warehouses and yes, big power plants. We tend to make things as big as physics lets us do, because of economies of scale. For power generation specifically, big things tend to be more efficient, thanks to the square-cube law. For example look at big ship engines, they use specialized piston engines with cylinders you can fit into, not dozens or truck engines, even though the truck engines would be a good example of modularity.

And speaking of the "mainframe era", in a sense, that era was more distributed/modular than today. Companies had their own mainframe, whereas nowadays, it is centralized in huge datacenters. The servers themselves are modular, because we can't make a datacenter on a chip, physics get in the way, but having big datacenters help make economies of scale on cooling, power generation, security, etc...

I am not against SMR, they are an option worth considering, but if I had to bet between SMR and conventional, large size nuclear reactors, I'd go conventional. Someone mentioned China as taking SMR seriously, and yes, they do, but they are also building lots of big nuclear power plants, and they are doing very well at it.