Michal, I think that your complaint is caused by a misunderstanding of how package maintenance happens in Ubuntu. I’ll try to clarify it, based on what I understand (if you know better than me, don’t hesitate to comment).
The part of Canonical maintaining the distribution is organized into teams (full list here), like Kernel, Foundations, Desktop, Mobile, Server, etc. Most of those teams have mirror-teams in the community, like the Ubuntu Desktop team. Those teams take care of subsets of packages in Ubuntu, of relevance to the respective teams. (This is orthogonal to package upload rights, which are managed with the Ubuntu Core Development Team, and the Ubuntu Development Team ; there’s a proposal to change that so that package upload rights are based on the first set of teams).
However, there are some packages (probably more than 70% of the packages in Ubuntu, including main+universe) that are of no interest to any particular team. Those packages are maintained on a best-effort basis by all the Ubuntu developers (inside the loosely defined MOTU team), and focus is usually on not diverging from Debian, to make their work as easy as possible. It’s very similar to what we do in Debian with orphaned packages: sometimes, important bugs get fixed, because someone complained loudly enough or a developer ran into the bug and did a QA upload ; but usually, we don’t really do any bug triaging. Of course, there are some packages in Ubuntu that are not maintained by any “core” team, but still have someone that cares about them. They are more the exception than the rule.
So, yes, obviously, you will run into packages with lots of untriaged bugs, sometimes even with patches. And those bugs and patches are rarely being forwarded manually to Debian, simply because nobody cares about those packages in Ubuntu. In an ideal world, with infinite resources, this would not happen, of course. But realistically, this is not going to change anytime soon.
There’s a link on the PTS to the bugs of your packages in Ubuntu. The idea is to allow an easy access to the bugs reported in Ubuntu, which are likely to be also relevant to the Debian package. You should probably feel welcomed to triage the bugs against your package in ubuntu, if it makes it easier for you to monitor them.
There’s some noise in the Ubuntu bugs, of course, but more and more often, by looking at the Ubuntu bugs, I find important bugs in my Debian packages that are not even reported in Debian yet.