Here's a good summary of the issue: http://homepage.ntlworld.com./jonathan.deboynepollard/FGA/de...

A bad thing about systemd and where we are now is the ever-changing API that is mentioned, which hampers alternatives to systemd.

But, that is where we are now, Debian isn't in much of a position to change that, and forking probably isn't going to help with that. Debian wasn't ignorant of that either; these issues were discussed at length in the tech committee debate that originally settled on systemd being the default for jessie.