The list of annoying, unnecessary or inferior features  the new Firefox versions is getting longer. To get back to where it was about a year ago, you already have to tune it by putting back the status bar, disabling animations, opening tabs at the end. Add to that the disabling of the "switch to tab" feature, which does no longer let you pick a second tab from history if you already have it open elsewhere. Usually, you can disable these things from the about:config page, however for this one you need a third-party plugin to get back to normal. It's called "Switch to Tab no more".