Oh no, that's absolutely needed, because yes, we can develop with git sending patches via and ML, IF people know your project exists. That's why we need usenet where we can have a freshmeat.net and co equivalents to makes new projects visible. This very visibility is the reason why GH and co are popular, because devs attract others devs who casually found their project, and Usenet have a proven history of making knowledge travel fast.
About people knowing how to develop with an ML and patchsets, the issue it's not much in people but in the substantial absence of modern MUAs though ALSO for this simple automation. I use notmuch-emacs, but I can't propose it to most others simply because deciding to keep maildirs on their own homeservers, most do not even have, muchsync-ing against it, maybe also adding a web-MUA and a dovecot to serve the mails on the go also on mobile, ... it's simply way too much work.
That's why again we need NixOS/Guix System to simply say "hey, import this code, change few parameters and there you go your homeserver FULL setup with anything, just choose other modules to discover the FLOSS world.
This damn need usenet to allow newcomers discovering what we have, learning how to use, and learning a model almost all have never known or forgot for some crappy colorful WebUI/walled garden.
We do not need copies of the big tech stuff, we need to show better stuff from a model where big tech can't even exists economically. That's the FLOSS superiority and strength no company can dream to match if it's done on scale.