This is a slightly edited copy of the mail sent to debian-devel@.
TL;DR: see https://trends.debian.net and https://trends.debian.net/#smells.
Following this blog post I did some work on setting up a proper framework to graph historical trends about Debian packaging practices. The result is now available at https://trends.debian.net/, and I’m confident that I will be able to update this on a regular basis (every few months).
Additionally (and much more controversially I guess :-) ) I also added an analysis of “package smells”, such as “not using dh”, “not using a recent debhelper compat level”, “not using a 3.0 source format”, etc. I understand that in some cases there might be good reasons to keep those “smells”, but I find it valuable to have them presented in a more actionable way to fix the cases that should be fixed. So there’s a list of smells, sorted by maintainer/uploader.
Given that Debian is currently frozen to prepare the buster release, this is a bad time to start fixing those smells, but I will send a reminder to debian-devel@ once buster is released. (It’s interesting to see how the number of smells plateaued during previous freezes).