I don't participate in any mailing lists since at least 2008 and I'm pretty sophisticated. What constitutes "works" is that they (Linux Kernel working group) have a very primitive forum (mailing list) wherein there is no recognized pressure to change. People still use HAM radio because they "work" but that's not the optimal way to collaborate.
Does it? I find it really cumbersome. We were just interacting with it the other day and found it annoyingly baroque. There's a lot of assumed knowledge and I've read a fair bit of documentation and have been following Kernel development since before my career.
It "works" for the people who it works for and that's it.
I don't have to suggest anything in its place. I'm just relaying that I've actually interacted with it for years and have found it cumbersome, and I don't think it's fair to say that it's "worked" as if it hasn't made first-contributions significantly harder for a lot of people.
At this point I might suggest Gitlab, but I don't really feel like having a back and forth about what may or may not be ideal about that.
Give it a few more decades.