I don’t think it matters what tools you use as long as it works.
That would be true if other systems and services depend on them. Would have been nice to come out with a standard and designed systemd around that standard. Then you pick the tool you want that follows the standard rather than be tied into systemd.
Worth noting is that a process not managed by pid 1 isn’t really a thing you want generally
I would disagree. A compromised Docker doesn’t mean i have access to things managed by PID1. The entire control model is based around moving your publicly available services further away from something with the highest level of access. Be it users or processes.