Where possible, overwrite CMS templates, 3rd party scripts and plugins that do not adhere to these guidelines.
Hard to implement
13 High impact score
Pre-made templates should never be used in their entirety. There are lightweight CMS templates out there (Susty, Granola, Underscores, and similar), but even these can be stripped back further; remove any excess code, calls and libraries where possible.
The more thorough version of this principle is decoupling your CMS from your rendering layer entirely. A headless CMS (e.g. Contentful, ContentStack, Umbraco Heartcore) feeding a static site generator produces a website with none of the traditional CMS template weight; the CMS creates and stores content, a static build process turns it into flat files, and those are served from cheap, fast, low-carbon cloud storage rather than rendered live on every request. It’s a heavier lift than trimming a template, but it removes the templating problem altogether rather than managing it.