Personally, I think that it's the copyright assignment that's the biggest barrier. For someone who figured out how to use Emacs, it shouldn't be very hard to figure out how to use a mailing list too.
It is so discouraging that I stopped working on the Emacs core [1] altogether: your contributions won't be acknowledged at all, even if someone volunteers to rewrite your code from scratch.
[1] I've been hacking some GUI-related features, but I'm not motivated enough to complete them. I also tried to write patches for my bug reports, but alas, my "CA-free" quota is already used up.