Performance matters nowadays a lot. Not only for SEO but also with every 100ms a page takes longer to load, you make typically less revenue etc.
To let users monitor and improve performance, it would be great to track more performance metrics such as the DNS load time (
performance.timing.domainLookupEnd - performance.timing.domainLookupStart). Also the time it took to render the page in the client, the waiting time on the server, how much time was spent during the "ready event" and during the "load event", etc.... be very useful. See https://developer.mozilla.org/en-US/docs/Web/API/PerformanceTiming
This helps to identify if improvements on performance really work and which effect it has on goal conversions, sales, revenue, etc.
This shouldn't be too complicated to implement but requires likely new DB fields in log tables unless we develop a new log table for this. Because an update for the existing log table be very slow, this would be something for Matomo 4.