What I think they overlook is that, right now, it is impossible to recommend Firefox in any case, because it performs so poorly compared to Chrome that no one will take such a recommendation seriously.
I've been using Firefox since back when it was still called Phoenix. I intend to go on using Firefox for as long as it still exists. But it's been a struggle, these last few years. Having to kick over a primary application platform, losing effectively all state save what programs are running, and reboot it every day or two, because otherwise it gets so slow that it's entirely unusable, gets real old real fast. People like to make jokes about Emacs, but even it doesn't do this! My Emacs sessions last months, and die only when the machine loses power or I hose up the environment so badly while experimenting that it becomes unrecoverable without a reboot. And Emacs is thirty years old.
I don't want to switch to Chrome. Its UI sucks and I'm no fan of Google. But if Firefox keeps getting worse, I'll have to. So I am absolutely delighted to see Mozilla making real and tangible progress toward solving that problem. If doing so means deprecating an ancient plugin API that's in any case dangerous and hard to use, I'm fine with that, especially since there is no reason in the world to believe that its replacement will not eventually gain back most of the relatively few capabilities we're losing in the deprecation. Maybe I won't be able to customize context menus for a while. That's fine, if the browser regains the usability it's lost over the last ten or so years.
I understand not everyone agrees with this point of view. That's not a problem. But I should not like this point of view entirely overlooked by those currently proclaiming the imminent death of Firefox.