Yes, for the Chrome User Experience Report, it looks like the site that you mention does not have a sufficient number of visitors. This is documented here:
If you want to improve the core web vitals, consider visiting
https://pagespeed.web.dev/ - while the upper section of
its analysis does not have data (as discussed, based on number of visitors), the lower section "Diagnose performance issues" uses lab tooling (simulated, not real users) and therefore it has hints.
E.g., at the moment I'm reading this for the homepage you mention: "Enable Remove
Unused CSS in 'WP Rocket' to fix this issue. It reduces page size by removing all CSS and style sheets that are not used while keeping only the used CSS for each page."
To measure the core web vitals from field data (actual users), you could use RUM (Real User Monitoring). Some pointers from
web.dev:
Good wishes!