It’a not that simple. Older content might not have webp images variants available, or styling might be optimised for newer stuff and cause old pages to reflow,

It’a not that simple. Older content might not have webp images variants available, or styling might be optimised for newer stuff and cause old pages to reflow, and many other things like that. Key web vitals change over time and it’s often a mix of content, styling and scripting that needs to be optimised to fix CVW issues. Revisiting old content and rebuilding old assets might not be worth it. I’m not talking from a perspective of maintaining a personal blog, but a product web site that currently gets about 1.5 million visits from organic search per month. It’s not CNET, granted, but not a trivial site either.