> Can you elaborate how engineering on an open source product is prevented from doing the right thing™ by management?

I have a purely speculative and very pessimistic opinion that is to not compete too much with Chrome and Google, so Mozilla does not antagonize with the source of their money while still providing Google with a "but we have competition!" card that they can use to prevent governments from treating them as a monopoly.

This is almost a conspiracy theory but, hell, that's the only explanation I have for so many management failures and aversion to their userbase.

Because the vast majority of engineers working on the code base are employed by the management. They can't just do their own thing & remain employees. Plus the FF code is controlled by Mozilla corp. You have full freedom (as an outside contributor) only in the sense you can always fork, not that you can somehow force Mozilla to accept your patches. Same as Android and all other major OSS controlled de facto by corporations. True community led OSS is quite rare, especially among the market leading software among their category.

Because the person in charge of the repository said so?

Just because something is open source (like most of my projects are open source), that doesn't mean the project owner must now accept any changes anyone in the world wants to make. Particularly when this 'anyone' is being paid by a company to implement what this company wants in a repository owned by said company.

That's not to say that open source is useless: if it were closed source, you wouldn't have been able to tell that the code is in the repo, just not activated, and you wouldn't have the option to fork it and enable it yourself and make your own custom build (freedom to study, modify, redistribute, and run), or pay someone else to make this change for you. Try that with Microsoft Windows source code, you can't study or modify that or even run it without permission.

Getting fired.