well the article had some issue's especially around coreos, but it's good that somebody points it out.
Actually CoreOS produced pretty stable stuff: etcd, fleet. Actually with fleet/etcd combined with some cgroups i see barely a reason to use docker, I mean on Cloud's its actually another useless layer, at least for me, maybe not in Google scale.
container engines provide apis that orchestration softwares use to manage containers in all kinds of ways. In small setups with not much logistic going on i guess you can manage everything with fleet and some systemd units
Actually CoreOS produced pretty stable stuff: etcd, fleet. Actually with fleet/etcd combined with some cgroups i see barely a reason to use docker, I mean on Cloud's its actually another useless layer, at least for me, maybe not in Google scale.