I’ve not been tracking them because I tend to only collect dirt on the greatest of evils. What comes to mind:
default search engine: Google (this is what that Google money is for officially)
Mozilla gave the boot to a lot of plugins and imposed some kind of control-freakish trust mechanism. Plugins/extensions were evicted from the plugin repository and they made it hard for plugin creators to distribute their plugins. I lost several very useful plugins when Mozilla took this controlling protectionist stance.
MAFF ditched. Mozilla abandoned a good format for archiving websites. I had a lot of content saved in *.maff files which Mozilla dropped direct support for and at the same time they blocked MAFF plugins.
Without Firefox, Google would be easily targeted with anti-trust actions. Google props up Mozilla just enough to be able to claim they have “competition”. Google can be most dominant when it has a crippled competitor under its influence.
Google killed the free world JPEG XL format. When a browser as dominant as Chrome withholds support JPEG XL, there is then no reason for web devs to use that format. Google did this because JPEG XL competes with a proprietary Google format. Firefox does not support it out of the box either, likely because of Google’s influence. Firefox users can enable it by going through some config hoops, so if Chrome alone did not kill it, that certainly would.
I vaguely recall a slew of Mozilla actions that were anti-thetical to privacy and user interests which caused me to move them from “a decent browser” to a “lesser of evils”. Hopefully others have better records of Mozilla’s history.