Browsers are supposed to be the new "platform" of the future. But their source code is so gigantic and inaccessible. A regular dev can't just pop in and help out, they have to learn a ton about internal browser infrastructure that they don't really deal with, and the learning curve is very steep. Contrast this with Linux, where most of us know the command line and can create/edit command line utilities much more easily.
Well, the same is mostly true of traditional operating systems.
On the other hand, traditional operating systems support a myriad of local development options on top of them, whereas with browsers you're, at some level, using HTML/CSS for display and JavaScript for logic. Both of which I still find to be unfortunate despite how far they've evolved.
This is absolutely an important issue. Brian Bondy from Mozilla's platform engineering team put together an awesome little website called Code Firefox (http://codefirefox.com/) with a series of 1-minute videos that teach you everything you need to know to get started. :D
To be fair, the Linux kernel is similarly opaque (although I agree that browser engines should make more of an effort to be clean and easy to understand—something we're working on with Servo!)
I think the right analogues to userspace utilities are something like Angular or jQuery, which are much easier to understand than the browser "kernel".
