A Magento 2 frontend can have excellent backend TTFB and still feel slow, because the browser spends its first seconds downloading and blocking on stylesheets and fonts before it can paint a stable page. Web fonts and render-blocking CSS are where the Core Web Vitals metrics you spent weeks on —...
Source: [Dev.to](https://dev.to/magevanta/magento-2-frontend-performance-web-fonts-critical-css-and-render-blocking-resources-4c7c)