Rust required to build Gecko
Gecko is already dependent on a lot of things so adding Rust might not be that big of a change, but IMHO a long and large list of dependencies and complex build processes are what can really put off those wanting to contribute to browsers (among other software) by fixing bugs or whatever else. I have personally experienced a few times where it was easier and faster to just patch the binary than figure out how to compile everything from source and go through the whole configure/install/etc process again.Especially with browsers, which not everyone agrees on how they should be and desires to customise, only to find that the option to do so has been removed or a source change must be performed, is subsequently delighted to know that it's open-source so they should be able to do it easily, but then get overwhelmed and give up after they realise the effort needed just to build an unmodified version of the software themselves. They then fall back to merely complaining on the Internet, and reluctantly accepting their "fate"... somehow, I feel like some of the visions of open-source didn't quite turn out as well as hoped.