Hurd developer here. You are spot-on. The Hurd solves a problem today that Linux (and all the other monolithic systems) will never solve: Fault containment.
It should result in a more stable and secure system, however, it doesn't run on 64 bit chips... and runs on only a few pieces of 32 bit kit.
Are you saying the Linux kernel will show issues if not running in cooperation with systemd? Where's the tight coupling?
Got it, but that's systemd requiring the coupling not Linux (which I assumed you meant "the kernel"). If we're talking about distros, then yes, there is a very high coupling of the ecosystem to systemd. The kernel continues to be unaffected, mostly.
The HURD design was always more elegant, and should result in a more stable and secure system. That's absolutely a project worth pursuing.