Laugh is most of the automated "tools" -- pageSpeed and Lighthouse for example -- are actually POOR metrics. Don't get me wrong, they're a good starting place...

But looking at a networking waterfall, counting the number of separate files (which can be more important than file sizes!), testing from restricted / throttled / low bandwidth environments, and simply leveraging what's between one's ears is a thousand times more effective than what any "automation' could provide.