Rust and servo were how they were innovating, and where a lot of the competitive features came from. By firing them, Mozilla made clear that they do not care about these things. The CEO is quite clearly a parasite hell-bent on extracting as much value as she can before bailing for the next victim.
The problem--and I feel the pain here deeply as a security person myself--is that that innovation was primarily along an axis (security) that no users care about (with a small bit of performance from concurrency, but there were clearly other ways to be faster), and was draining resources away from innovation that users cared about... which I'd claim was even going in the opposite direction: for many years now they have been continually tearing out the non-philosophical reasons I used Firefox in the quest to build a clone of Chrome, something the world doesn't have much use for as it already has Chrome.
Remember that the users still using Firefox are mostly technical and privacy fans that do care about security a lot.
Focusing on the mainstream user at this point will not help as they're already so far gone they don't even remember the name Firefox anymore.
They should focus first on making it and excellent browser for the users that still care. Then word of mouth will bring it back to the mainstream as it did the first time.
It's not even that they're building a clone of Chrome - Chromium is actually adding features like tab groups.
It's more that they're removing not-Chromey bits, not adding the Chromey bits, and removing Firefoxy bits like search keywords via bookmarks and the like.
As a Firefox user I disagree. Their work on Servo and Rust resulted in many performance and reliability improvements. WebRender for example came directly from Servo.
It's unfortunate that after those changes, the Mozilla team did not take criticism in public forums very seriously and brushed it off as noise. I personally stopped using Firefox after some of those "architectural" changes started producing "dead" tabs - the tab could not be interacted after load.
In place of "We're listening", users that complained got a "Works fine on my machine" bundled with a few rude words in places like Reddit. Not the core teams fault, of course.
Someone with more time can probably set up a scientific test of the performance claim even today - set up a bunch of Selenium tests to open JS-heavy sites in multiple tabs on older versions of FF upto current version using BrowserStack or SauceLabs.
The question is, would the work have been done sooner, or more effectively if they had just fixed the C++ code rather than spending a lot of time creating rust, only to rewrite said code?
I mean to this day (and i just tossed off a firefox build yesterday to see if most of what I was saying is still true), the firefox maintainers can't even be bothered to fix the tens of thousands of warnings that appear when built certain ways. That is a really low bar to cross with a C++ project, and they haven't even bothered. I've worked on projects where we had a recommended compiler, but we always spent some time assuring that the project appeared to work with the latest gcc/icc/whatever, because at some point those newer compilers would become the defaults, and also because they frequently pointed out issues in the code. Its just a cheap way to fix undefined behavior bugs.
So, I think the only answer to that is yes, that long stretch before they dropped the rust code was wasted time/effort.
