See https://news.ycombinator.com/item?id=13632352 . It's not a simple matter of just sending an email. You can't send patches via gmail (because it autoconverts tabs to spaces), and setting up a client is involved, hard (impossible for some), and should be totally unnecessary.

I despise this "I'm happy to exclude people too incompetent to do X" attitude. I often mentor people into FOSS. They start off pretty incompetent with the tooling. With a bit of nudging they end up making high quality contributions. A person's usage of email has no bearing on their, say, Python skills. Nor does a person's usage of GitHub. These are tools to get the job done, they are not the job themselves. Tools should be easy to use. Github isn't exactly easy, but it's much easier than patch MLs.