https://en.wikipedia.org/wiki/Firefox_version_history#Firefo...
Second thing: where do you see the application of the UNIX philosophy being actually useful and popular? It's not even popular in the *nix world - systemd, for one, breaks it in a big way, but is still wildly successful, maybe because it's doing many things, and it's doing them well. Another successful example is ZFS - top of its class, and it's many layers integrated to one. The power comes from the integration.
It is unlikely that anyone working on Firefox contributed to this.
* criticizing Mozilla for having profitable side projects, such as Mozilla VPN or Pocket that diversify their sources of revenue
* criticizing Mozilla for even the most innocuous types of browser monetization, like the ad for the Disney movie about Red Pandas
What exactly do you want them to do?