Every reactor and every plant is bespoke, even if they are based on a common "design" each instance is different enough that every project has to be managed from the ground up as a new thing, you get certified only on a single plant, operators can't move from plant to plant without recertification, etc
Part of that is because they are so big and massive, and take a long time to build. If we'd build smaller, modular reactors that are literally exactly the same every single time you would begin to get economies of scale, you'd be able to get by without having to build a complete replica for training every time, and by being smaller you'd get to value delivery much quicker reducing the finance costs, which would then let you plow the profits from Reactor A into Reactor B's construction
Nuclear submarine power plants are not in any way a technology useful for utility scale power generation.
To start with they use fuel enriched to weapons grade.
They aren't cost effective vs the amount of power produced, and the designs don't scale up to utility scale power.
Submarine plants are not some sort of miracle SMR we can just roll out.
The Navy is willing to page cost premiums a utility company cannot, because for the Navy it's about having a necessary capability. There's no economic break even to consider.