I've looked at it only briefly, but... From my (mostly Unix-ish) perspective z/OS looks a bit like as if MS-DOS have been continuously developed by a few hundre

I've looked at it only briefly, but... From my (mostly Unix-ish) perspective z/OS looks a bit like as if MS-DOS have been continuously developed by a few hundred people since the eighties. There are some nice things, but the overall system architecture is somewhat... nonexistant.