Ouch, telling people not to update... this wasn't a bug in 7.1. Perhaps consider your usage of @wp_rocket. This is also part of the risk of using plugins outside the official plugin directory, which has many alternatives that seemed fine on the 7.1 release day.
To all @wp_rocket users: we've identified a compatibility issue with WordPress 7.1 that can cause a fatal error on your site. We're working on a fix! We suggest not updating to WordPress 7.1 until it's released.
Please contact us if you are already affected so we can help you to
