> At least I can be certain that the interactions between the components are known and tested.

Oh good _lord_ you absolutely cannot. It has been my professional experience that Systemd Project is fractally complex, most of that complexity is accidental, and approximately no one on the project is interested in investigating and fixing the intermittent-but-showstopping problems that arise from that accidental fractal complexity. [0]

Poettering and crew really built the project a fantastic escape hatch with their whole "Your usecase is legacy and we're not supporting it." attitude.

[0] The mess of tools in the Systemd Project work fine until they very suddenly do not, and then the best you can do is bodge a workaround because you're very unlikely to ever get a fix for your problem. The folks that staff the project simply don't have the attitude required to work on and maintain a ever-more-sprawling project that aims to be _the_ userspace thing atop which every Linux distribution is built. "That's hard to fix/do. I don't care that you've had a working system for 10+ years, I'm not fixing the thing that's broken for you." is an absolutely unacceptable attitude for folks involved with such a project to have. [1]

[1] If the project was a little take-it-or-leave-it side project, that attitude would be entirely acceptable... encouraged, even! But because of the position in which the project willingly and aggressively put itself into, it's not a little side project.