I find the idea that a technology should be replaced simply because it is old to be very irksome. Those developers out there blindly contributing to the trend of replacing "tried and true" with "new and shiny" really need to take a step back and gain some perspective. Email works great for the vast, vast majority of users.
While I agree, the opposite is also an issue. Developers which either look down upon anything new as "pointless" or in some cases actively try to stop improvements. Looking at the kernel dev system, it works great, but it has its share of problems. I've never even thought about contributing to the kernel because of the work involved to just submit a patch, that process can be improved. Making it easier for newcomers,…
And that's an important difference. I feel that projects should allow newcomers to contribute through multiple channels. For tiny patches from newcomers, it doesn't really hurt to let them make patches on github, go through review (without annoying other folks with nitfix review emails), and mail the final patch to the list for them. Of course, as they start to contribute more, nudge them towards the "real" patch process. This moves them towards contributing the regular way without the process being one more barrier in the way of entry.
I've mentioned this in http://manishearth.github.io/blog/2016/01/03/making-your-ope... -- you can tailor your process for newcomers. Your current process is probably great for power users but might be complicated for newcomers, but at the same time a lot of what makes the process great really isn't necessary for the patches that most newcomers contribute.
Of course, all this works when the project actually cares about helping newcomers. As mentioned in the other comments, it seems like Linux doesn't care about this; it prefers to restrict itself to contributors who can (and want to) figure it out on their own. This could end up filtering out smart people who could have figured it out (but found better uses of their time), but that's their choice.
Not to say that projects which don't do this don't care about this. GDB has a pretty complicated process, but they're also very helpful to newcomers. I might work on providing an alternate workflow or a mentoring process at some point. Firefox is similar; the bugzilla-based workflow can be new and tricky, but there's mentorship. (Another thing I may work on improving at some point)