People.
But that does not mean ignoring search engines.
Good website copy can do both.
Search research can reveal the language people use, the questions they ask and the information they expect to find on a page. That information can help shape the structure and subject matter.
The mistake is allowing SEO requirements to overwhelm the writing.
If a keyword is repeated so often that the page becomes awkward, or paragraphs exist solely because somebody wanted another variation of a search phrase, the page is no longer doing its main job particularly well.
Search visibility gets somebody through the door.
Once they arrive, the page needs to communicate clearly, establish trust and help them decide what to do next.
Those are human decisions.
For a deeper perspective, read Your content sounds professional. But does anyone understand it? on Insights.