Are these sorts of general advice on how to do X even valuable today when you can put the details of your start-up into AI and get a more customized and moderately more thoughtful actions based on what your start-up does, who your customers are, etc?

Who's still going through these kinds of docs?

I know micro.so (I'm not affiliated with them) have documented how to build agentic B2B sales AI that you can download (if you give them your email address). https://www.micro.so/guides/sales