Kernel development shouldn't have a low bar, it should have a very very high one. Anyone that finds email a high bar for communication doesn't belong in Kernel development.
No, the former is enough. It shows that whatever their programming abilities they are prone to bike-shedding, so they are better avoided.
Also we are arguing backwards here. They don't make it intentionally hard to keep out new contributors, it's just not important in any way to make it simpler. The goal is to make it work best for the thousands of existing contributors, especially the gatekeeping subsystem maintainers.
Generally yes, but IIRC Linus has explicitly said that he likes the process being intentionally hard to keep out new contributors.
If you won't submit a kernel patch because you feel that email is unfashionable, then you're kind that should be kept out of the gate. Sorry.
The linked article explains at length why it works well for kernel maintainers. And since it does, why should kernel maintainers change it just to make things easier on newbies? It's much more reasonable to expect new participants to adapt to a workflow that works, than vice versa.
This is not "gatekeeping," it's just the reality that not everyone works the same way.
I get the feeling most people who complain about how "clunky" email is have never actually tried to submit a patch to LKML. If I could figure it out when I was a high-school student, a professional developer should be able to figure it out as well.
That's as intended.