Use Tor Browser if you want it dialed up to eleven. You'll quickly find that it's way more of a hassle to use, and also still pretty easy to accidentally compromise the security measures.
Of course Firefox isn't perfect; nothing is. But a 180 turn implies it's the opposite of perfect now, and it really isn't - especially in a world where basically every other browser is waaaay closer to that.
But also keep in mind that it couldn't exist without Firefox/Mozilla existing. A world in which more people use Firefox over Chromium-based browsers is a better world.
A Mozilla dependent on Google seeing value in Firefox sending searches their way is at minimum as good as one in which Mozilla doesn't exist and everybody uses Chromium-based browsers, by definition - and in practice, way better.
But yes, more non-Blink engines in use in general would also be a better world. Alas, that, too, isn't the world we live in.
Firefox needs a 180° turn to full privacy out of the box. - Feddit (feddit.de)