A refresh may be enough
If your platform works, your pages are easy to edit, and your structure is sound, start with your copy, navigation, images, and calls to action. A full rebuild is not always necessary.
When a rebuild makes sense
Consider a rebuild when essential features are missing, the site is difficult to maintain, or the platform prevents meaningful improvements. Compare the cost of patching those limitations with a planned migration.
Start with a clear scope
List what must change and what can stay. Review existing pages and important URLs before making changes. An audit can give you a practical sequence instead of a guess.