Dropping support for legacy extensions absolutely gutted what made Firefox different from every other browser. I'll use Firefox 56 and NoScript until the end of time before I use a browser with tabs above the address bar.
Although it is possible to move the tab bar using user CSS [1].
You're also missing out on a much faster browsing experience with the newer versions. In the older version I remember the scrolling lagged when I opened a new tab in the background, that hasn't happened in a while.
[0] https://en.wikipedia.org/wiki/Fitts%27s_law
[1] https://www.userchrome.org/what-is-userchrome-css.html#movet...
Usernumbers went something like 250->300->275 Million. Seems they are somewhat stable in numbers.
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
#TabsToolbar {
-moz-box-ordinal-group: 2;
}