This doesn't excuse many of the other things they do, like (often badly) patching upstream code and not sending the patches upstream.

It's one thing when you simply don't have the resources or the manpower to respond to all the bugs. That's understandable -- you deal with the really important ones and oh well.

It's totally another thing when even the ones you deal with, you deal with poorly. Especially when, more often than not, upstreams tend to be helpful, especially with large distributions like Ubuntu. A bad patch can always be made better. No communication leaves things exactly as they were. A bad patch and no communication makes them even worse.

Also, since Ubuntu aims at regular users, the quality of their bug reports is probably also lower on average than some other distributions.

The few times I bumped into an Ubuntu bug report, it was typically very long, light on useful data points for debugging/reproducing, and had several unrelated bugs in the same comments.