Perhaps it isn't inactive. There were 70 messages there since Monday and it's now Sunday.
Perhaps all the popular modules have their own mailing lists or other forums.
Meaning by definition, there won't be many messages.
But even some well-known modules like ingy's don't have forums. In particular, cpanforum didn't spring to mind, when I wanted to post something about Test::Base somewhere.
Perhaps I should have sent it to email@example.com.