You can do it with Classic Theme Restorer. https://addons.mozilla.org/hu/firefox/addon/classicthemerestorer/ Moreover we are not trying to copy anyone, we are sorry for any inconvenience caused to you. If you feel strongly about the new changes I would suggest you to provide feedback on https://input.mozilla.org/feedback for the people who decided on the changes to actually see it. Please keep in mind that Firefox is a work in progress and your feedback is very valuable for us to understand what can be done better!