I only had undergrad EE training so maybe I’m out of touch with what’s done in industry. But, I think most human engineers mostly don’t design novel circuits either. Chips come with specification sheets that have some reference implementations. So obviously somebody at the company designs that reference implementation, but I think most users stick pretty close to it…
Copy/paste (from reference boards or examples in the datasheet) is pretty common when starting a new design but if you don't then figure out what each connection and external component are there for and adjust to your application (or sometimes figure out the part won't work for you) then you quite literally don't know what you are doing.