Surely people have found patterns that work reasonably well, and it's not "everyone is completely on their own"? I get that the scene is changing fast, but that's ridiculous.
You can do that in conjunction with trying things other people report, but you'll learn more quickly from your own experiments. It's not like prompting a coding agent is expensive or time consuming, for the most part.
But your codebase is unique. Slop in one codebase is very dangerous in another.
I ran a small python script that I made some years ago through an LLM recently and it pointed out several areas where the code would likely throw an error if certain inputs were received. Not security, but flaws nonetheless.