A good mailclient allows a skilled user a much more efficient communication than most forums.

> It probably doesn't really change that much in this scenario but with a forum or any other topics-based platform you can at least just close and ignore these things without it affecting everyone else.

True, external moderation is a benefit of centralized platforms, but a mailclient allows personalized moderation, which allows with a well organized list to only filter out anything you are not interested in. Usenet had the benefit of both, a centralized platform with moderation, and powerful clients for further personalization. Too bad it died for most usages.