I don't think that's the whole point. If all you care about is packaging your code in a container, then you don't need Docker. That was solved long ago. Docker simply adds a nice API on top which allows you to package, ship, and manage your apps in the same exact way.
By using something like Docker Compose, you can explicitly define each container and the relationships between the containers. Then, you can start/stop groups of containers (an application stack) while still retaining some component isolation and the ability to upgrade and scale containers independently. All of this is defined in a relatively simple YAML file, which can be committed to VCS and tweaked. I can't tell you how awesome it is to find repos on Github that have use docker-compose. Even complex apps with many pieces can often be launched with a single command. It's easy to take these stacks and tweak them to your needs, adding/removing/changing components as necessary.
Since Docker provides a standard way for managing any container, orchestrators like Swarm, Rancher (my preference for small-medium clusters), and DC/OS can take that functionality and scale it across many hosts. You can get a birds-eye view of your Docker cluster (all apps) or drill down into individual apps and their components. Each container is a uniform piece and can be controlled, scaled, updated, audited in the same way. Throw a UI in front of it and now you can manage applications that you know nothing about. That's great for developers that manage just a few apps, and it's incredible for enterprises with thousands of them. If you don't want to think about infrastructure at all, then you can use a SaaS Docker provider. Obviously there are pros and cons to each approach, and there are some remaining challenges.
Docker isn't perfect, especially in regards to storage and networking. Distributed storage isn't simple, but a lot of progress has been made with volumes and volume drivers. It's not as easy as it needs to be, but the general direction seems to be good and with the proper tooling I think this will be less of an issue.