In the cases (which happens more than you might think) where an upstream developer has actually got really good packaging, I've usually taken the approach of tidying up the last few details and committing back and then mentoring them for a while with them doing the majority of the work and I just double check and upload it.
The level to which people are willing to work on it varies from accepting patches that affect the distribution package version (e.g. hardcoded paths or porting issues) to actually doing the packaging.
If you're interested in helping out with Debian: https://www.debian.org/intro/help
If you're an upstream developer and you'd like your package to be in Debian: https://wiki.debian.org/UpstreamGuide
I am upstream for some of my packages and I don't provide the same debian/ directory upstream as I use for Debian.
I've heard time and time again that there are issues with Debian's version being out of date, but this doesn't have to be this way, at least not by policy. If there is a backport maintainer (doesn't even have to be the same person working on unstable) then the latest version can be installable within a stable system giving you the latest and greatest of the applications that need it with a stable base underneath.