What's up with Ubuntu's handling of bugs?

[S.]

In my opinion, one of the most important aspects of an open source 
project that distinguishes it from closed-source software is the way 
that the project handles bug reports. I try to be diligent about 
reporting bugs, and my hope is that the project will try to improve 
based on the bugs that I report.

However, I have noticed a disturbing trend in Ubuntu toward completely 
ignoring user bug reports. I am by no means a developer, but I am also 
not a beginner, and I have been using Ubuntu ever since its inception at 
Warty 4.10. In the beginning, Ubuntu was extremely respectful of its 
users' bug reports, with a prompt, human-generated reply to each and 
every bug, graciously thanking the user for taking the time to report it 
and asking for any additional information needed to triage the bug. Fast 
forward to recent years, and I'm now seeing a complete change in 
Ubuntu's attitude toward bug reports, which now borders on disinterested 
and apathetic. For example, since the beta and subsequent release of 
15.04, I reported 8 bugs. Of those 8 bugs, only 1 received a human 
response. And now during the 15.10 development cycle I have reported 5 
bugs, several serious, and I have received 0 responses. A quick review 
of the recent activity in the Ubuntu bug tracker seems to indicate that 
I'm not the only one who is being ignored.

So, what exactly is "open" about Ubuntu, if all their development 
happens behind closed doors and they don't care about their users' bug 
reports? Is the current traditional release of Ubuntu essentially being 
put out to pasture, with development only happening on Ubuntu Phone and 
Ubuntu Snappy? Or is Ubuntu getting a bit too big for its britches?

Other distros are significantly better at handling bug reports. My 
experience with openSUSE was considerably better in terms of bugs being 
promptly handled. And Arch also seems to take each and every bug report 
very seriously.