Most inherited WordPress sites are slow for the same handful of reasons: unlazy hero media, page builders emitting nested wrappers, unbounded plugin scripts, and fonts loaded like it is 2016.
Before a redesign, we measure LCP on real templates, kill render-blocking assets, constrain image sizes, and audit plugins for duplicates. Caching and a CDN help only after the HTML is honest.
The goal is not a 100 on a vanity URL. It is a site that stays fast when an editor publishes a new campaign page next Tuesday.