We have dependency management built into the package managers which hides that from us these days. Unix and Linux before package managers was kind of a pain. Now, I will totally give you that it was nothing like the "DLL hell" of Windows.
Frankly i think package managers are part of the problem, rather than the solution.
From personal experience using a less elaborate variant of what nixOS/Guix offers (Gobolinux), ld and friends are quite adept at getting multiple lib versions sorted via sonames.
But package managers do not use anything like sonames for resolving dependencies.
This because foobar-1.0 and foobar-1.1 can't be installed at the same time. Instead you would have to do something like foobar-1.0 and foobar2-1.1, even though foobar2 is actually a minor upgrade to foobar.
This because the logic of most package managers balk at having two packages with the same name, but different versions, installed at the same time.
Then how can be that an incentive for Docker's adoption? Honest question; if, as you say, this is a solved problem thanks to package managers.
I can't even remember the last time I had a real dependency problem deploying an application (using Debian; and CentOS before that), other than myself not doing things right (read: installing RPMs I found online and I shouldn't install).
Well I wasn't originally speaking wrt Docker, but Docker doesn't magically lose all the hard work done by package managers. You have total access to them in your containers.
