So, looking at this rationally, consider your favorite lightweight window manager or desktop environment for Linux. Is it fully internationalized, including support for CJK input methods? Is it fully accessible to users with disabilities, e.g. blind people and people with mobility impairments? Does it auto-mount USB thumb drives? Does it do all of the other things I'm not even aware of that are required for a fully usable desktop environment covering a wide variety of machines, users, and use cases? AFAIK, the only Linux desktop environments that come close are GNOME and Unity.
Basically, the world is complicated, so real-world software has to be complicated too.
It sounds like Atom could still use some optimization though.