You're just whining about minor cosmetic changes. The reason why Firefox lost share is because for a long time it was much slower at JavaScript, it had memory leaks, the interface would freeze when doing anything, pages didn't render quickly, and so on. None of that was something that Mozilla could easily fix because it was baked into the DNA of the browser.
They have put in the hard work to fix these things. Regular JavaScript in Firefox is as fast or faster than in Chrome and asm.js is much faster in Firefox. Memory leaks are almost all gone. The interface freezes sometimes, but not nearly as much. Pages render much faster.
The real problem for Firefox is not the interface changes that people like you whine about, it's mobile. Now 30% of traffic is mobile and Firefox doesn't have an app for any Apple mobile devices and is effectively excluded from Android by Google's Microsoft-like illegal anti-competitive licensing deals with manufacturers (you can get the app, but it's not preloaded and only a few geeks ever would). They're also up against a massive advertising campaign, with every Google property having a huge pop-up like ad telling users to use Chrome. Chrome users don't see this, but Google is doing everything they can except adding the words "or else".
Mozilla is doing a great job with Firefox, but they are up against a billions-dollar corporation that has set its sights on owning all the means to access the web that is spending hundreds of millions of dollars a year and is willing to break the fair competition laws to do so.