As a Debian Developer I often find myself throwing away the upstream Debian packaging and starting from scratch. It's not that it doesn't work but that it doesn't fit with Debian policy and so is not easily included or modified without basically starting from scratch anyway.

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