Okay, I can see where you're coming from. The deployment system within my company uses a "virtual environment" or "sandbox" model, and it does have its advantages. However, it also creates its own complexity and coordination problems, which I think are easy to underestimate if you haven't used such a system on a large scale. If I'm a library developer in this system, it can be quite hard to get updates to my library deployed to all the relevant application environments, even with the help of an extensive system for tracking deployments and dependencies.
Ubuntu uses the same packaging system (and almost all of the same packages) as Debian, and they have no problem releasing on schedule. Debian does have a problem (note: I am a Debian developer), but it's not a technical problem and does not have a technical solution.