You're writing for an imaginary "everyone" — no persona, no defined reader — so you're serving no one. Different users need different docs at different stages in their journey with your product; without a persona, the doc doesn't fit anyone.
Why it matters
Writing for everyone means the tone, level, and structure don't match any real user. Developers want quick reference; new users want step-by-step. One doc for "everyone" fits no one. Users can't find what they need or it's the wrong level — so they contact support. The answer was in the docs; the doc wasn't written for them.