Throttle your connection and use a machine with low ram, and you'll soon find most websites are unbearably slow.
Firefox: https://firefox-source-docs.mozilla.org/devtools-user/networ...
Chrome: https://developer.chrome.com/docs/devtools/device-mode/
I understand you leave money on the table, but you would spend less on support and less money trying to get your website to be 200ms faster to load. This is speaking from an Indie Hacker perspective. This could be potentially worth millions of dollars for a bigger business.