I haven’t seen that paper before. The ones I remember were blogposts or web pages. In fact, this may be what I was remembering: www.gnu.org/software/hurd/faq.html Particularly the part about what happened with the port to different microkernels.
IIRC NeXT and OSX use Mach, but they don’t use it as intended. I think they’re mostly a BSD kernel with Mach functioning as an interface to userspace.
Hurd actually used Mach as a microkernel, and moved most functionality to userspace daemons. This meant that Mach’s performance issues, at least the ones related to IPC, affected the Hurd a lot more than OSX or NeXT.
And yeah, I think developer interest was the biggest thing that held it back.