In this case you could still pick homebrew as your package manager of choice. It works pretty well, is available cross platform (https://github.com/Linuxbrew/linuxbrew) and is far more simple than docker. You just have write a short shell script which installs all the dependencies via brew when not installed already (much like you'd do in a Dockerfile).
Is Docker that difficult? The Dockerfile is a nice single file that defines all container dependencies and then it's three commands (build, create, and start) to be able to easily work in the exact same environment for dev, qa, and production regardless of whether the host is running OSX or a flavour of linux.
But you can install brew in a subdir. For some projects i do exactly that. Project/.brew. I have a project/bin/activate which puts ./.brew/bin in your path. And there you go: postgres9.5 for this project and postgres 9.2 for that project. Still no isolation though. And having pg installed in a docker image is not a good example... But you getthe point :)
