Mozilla lost its way
Firefox needs to regain what it stripped out so that it can compete by having actual functionality other browsers don't have, rather than riding on the coattails of Tor Browser innovations by adding GUI buttons to access about:config knobs every 3-4 releases. Most of the "new" Firefox privacy features came about many moons ago and of those which average users care about, they also exist within other browsers as extensions. Rather than playing to their strengths, they've emulated what Google Chrome does by stripping out key functionality and letting other big corporations dictate new standards.
I blame a lot of this on Mozilla forcing Brendan Eich to resign for his personal political opinions and replacing him with some rando lawyer with a BA in Sinology. While their former leader had some terrible stances on issues outside of his expert knowledge domain, he at least knew how to develop new technologies for making web browsers competitive. His leadership led to Mozilla killing off Internet Explorer while Mitchell's has led to Chrome killing Firefox.
Here's a list of key things Mozilla could be doing right now to gain greater market share:
* Integrating Java Applet and Java Web Start support as a core feature with universal JRE/JDK support (this would make it a must-have for accountants and IT)
* Adding support for client-side language bindings (such as Python) to pave the way towards cleaner, more maintainable websites with lower resource use
* Native TOTP, HOTP and portable virtual FIDO2 support. Basically, take Windows Hello but make it stateless, adding some additional checks for legacy 2FAs
* Implementing the functionality of the top 20 extensions in use.by default (ad blocking, video downloading, screenshots, grammar checking, proper dark mode)
* Fixing the mess with policy enforcement. It's a crap web browser to implement in a corporate environment, which means workers wont use it at home either
Right now, people only need modern Chrome/crEdge with IE Mode as a fallback. As a sysadmin, I have no need to deploy Firefox any more and it has no killer feature which will convince me to pick it over deploying a Chromium-based browser. In fact, Mozilla uses a terrible system for mandatory policy enforcement which puts me and others off using it. Right now, the systems I look after all have adblocking, phishing protection and password, history, settings syncing by default thanks to simple GPOs, while also providing the old Trident rendering engine for Java and Silverlight support on the few websites which still need it.
Make people need Firefox for things again. Even if it's only as a secondary browser!