Both failure modes are common
A site only developers can change goes stale, because a copy fix waits for a release. A site anyone can restructure loses its coherence within months. Most companies have experienced one and overcorrected into the other.
Split by risk, not by seniority
Text and images inside an existing structure are low-risk and should be broadly editable. Page structure, navigation, and templates are high-risk and belong with fewer people — the boundary is what a mistake would cost, not job title.
Let people change what a page says. Be careful about who can change what a page is.
Constrain the tools, not the people
If the editor only offers the approved components and type styles, a non-designer cannot break the system by accident. That is the design system living in the code doing its actual job.
Protect the URL
Slug changes should require a deliberate action with a redirect created automatically, because URLs are the part other people saved and an editor renaming a page for tidiness can quietly break inbound links.
Keep the facts in one place
Prices, timelines and claims repeated across many editable pages will diverge, and divergence is what produces contradictory statements a model can quote. Store them once and reference them.
Make changes reversible
Version history and a one-click revert removes most of the anxiety about granting access. Content changes should be as recoverable as code changes, and when they are, the argument about permissions gets much easier.