If privacy is the ultimate concern, I can suffer usability.
I think the real issue is we've stopped advocating for privacy loudly and publicly. All the users know is convenience.
But with Firefox, all the UI choices are gone now, intentionally sacrificed on the altair of rewrites, UI changes, branding and some dubious security claims. You used to get the choice of vertical tabs (better on todays widescreen laptops), tree-style tabs, Buttons where you liked them, user-provided CSS customization for pages and the UI. Not anymore, all gone (they paid some lip service to some of the above concerns, but nothing relevant, and overall a massive downturn).
Now you only get the take-it-or-leave-it of one crappy and worsening Chrome clone UI.
I activated browser debugging, pressed ctrl + alt + shift + i and then hunted down the offending tab bar and put in "display: none" for it.
It gets harder and harder year by year though and on the tabstrip issue in Bugzilla there's at least one person who was annoyed and told me to not question peoples motives after I asked a simple question about it.
Anyone here working for Mozilla, I ask the same question here: are you overcomplicating it? I managed to get rid of that tab bar using a CSS hack, why can't we just get a function to apply that css, at least in developer edition?
That said, these days Linux is just more convenient than the alternatives for me personally. Same goes for Firefox (still).