I have also been writing for the web for over 20 years. This doesn't really mean anything though. That is why measures are all that matters. Bad measures are still monumentally better than no measures at all.

The sad reality is that most people writing for the web today cannot do so without a framework. They have no idea how the layers underneath actually work. If you want to understand performance you must measure for it in multiple different ways and have something meaningful to compare it to. All modern browsers provide fantastic performance measuring tools in their developer tools. Its how I got my OS GUI (in a browser) to execute as fast as within 60ms of page load.