I've often said that Firefox is the most user-hostile piece of free & open source software I've used. It is much worse than a lot of paid, proprietary software.
Open source ended up being exactly what it says: you can see (and change, with enough time and effort) the source code. Nothing more, nothing less. It doesn't say anything about the incentives of its authors and their alignment with yours.
I'd still rather patch the binary (which is actually largely a zipped collection of JS that implements most of the UI) than figure out how to compile Firefox from scratch.
Android (at least the AOSP part) and Linux is a similar situation.
