If your website content and copy don't heed your Big 3 religiously, they can repel visitors (The horror!).
Say you've decided on an inclusive tone, but your text is filled with jargon. You'll lose readers and quickly. This, though, is only one of many pitfalls.
To see more kinds of problematic copy/content — in fact, a comprehensive list plus excellent examples — we recommend Webdesigner Depot's brilliant article, "How to Spot and Avoid Web Copy That Kills Websites."
Your writer should be able to isolate these defilers in your existing text and avoid them in their own writing.