Our goal is to build performance tests that simulate real-world user experiences so that browsers have better tools to drive improvements for real users on real webpages. While it’s easy to see that benchmarks have improved in Firefox throughout the year as a result of this work, what we really care about is how much those wins are being felt by our users. In order to measure the user experience, Firefox collects a wide range of anonymized timing metrics related to page load, responsiveness, startup and other aspects of browser performance.

Source: Down and to the Right: Firefox Got Faster for Real Users in 2023 - Mozilla Hacks - the Web developer blog

Honestly, I’m considering using Firefox again.