I did not work with the nuclear regulators, but I worked plenty with other regulators. Like lots, maybe thousands of hours of interaction. I noticed the tendency among the industry people who interact with regulators to grumble that "they don't even know what questions to ask", etc. I always found that unfair. Of course, as a worker you'd always rather do something else than produce documentation for regulators, but I personally appreciate that the regulators have a job to do, and in my experience they do it well. In many cases I was simply amazed of how thorough they can be.

I spent some time looking at the NRC safety approval of the NuScale design [1]. You look at all those documents published there and realize that they are all necessary. You pick one randomly and open it at a random page, and you don't find superfluous things.

Now, when you have a review that takes millions of man-hours of effort, you'll find cases of irrelevant inquiries. I suspect however that most of these inquires were irrelevant only in hindsight, not because the NRC supervisors were incompetent.

[1] https://www.nrc.gov/reactors/new-reactors/smr/nuscale/ser-op...