True, Docker-compose has a lot more overlap with systemd.
But it doesn’t have system-level dependencies. For example, in systemd I can wait for a network interface to be up and have an IP assigned by DHCP. As far as I am aware, docker compose knows about the docker network and its own containers, but not the system more broadly.
Also, you will likely want it to run for a long time, so something has to trigger the docker-compose process to start and restart it. You might want it to restart in case the OOM killer knocks it over. That daemom stuff is what systemd is good for.
But it doesn’t have system-level dependencies. For example, in systemd I can wait for a network interface to be up and have an IP assigned by DHCP. As far as I am aware, docker compose knows about the docker network and its own containers, but not the system more broadly.
Also, you will likely want it to run for a long time, so something has to trigger the docker-compose process to start and restart it. You might want it to restart in case the OOM killer knocks it over. That daemom stuff is what systemd is good for.