I am -1 too.
I hear that focus on discourses was specific to python-committers. I think, that still could be the case, and we should not expand it to replace mailing lists now.
None of the modern tools seem to handle the scale, convenience of emails well for in-depth or prolonged discussion, along with the convenience and configuration of clients that we use. (May be I should try discourse with text only mailing list mode?).