I would say that the feature set is pretty powerful as is, and it shows in the earlier history (having worked with Mixins since before it was called Mixins). The history reaches further back than the first commit to having been developed for Mumfrey's own modloader (LiteLoader).
As someone else already replied, Mumfrey still practices private development and only pushes new code after his own extensive testing. He has long periods of "public" inactivity because code refactors and other changes can be delicate given the widespread usage of the library within the Minecraft modding ecosystem, and as such, he doesn't want the distraction that in-development can attract from said community.
As someone else already replied, Mumfrey still practices private development and only pushes new code after his own extensive testing. He has long periods of "public" inactivity because code refactors and other changes can be delicate given the widespread usage of the library within the Minecraft modding ecosystem, and as such, he doesn't want the distraction that in-development can attract from said community.