Hello. This extension is meant to be a global playback rate controller. If you see no value in that concept, the extension isn't for you.

There is also no way to differentiate between a user changing the speed through the site's controls or the site itself changing the speed. Often, sites revert speed back to 1x. How do I know you intended to change it?

The only way for Global Speed to be sure of your intent is to change the controls through Global Speed's menu or shortcut keys (A-S-D keys by default).