You probably wasn't paying attention when Job was running things.
OS X 10.1 was a mess -- it took until several updates to become somewhat usable. The Finder was half-arsed for a decade. Mail.app had several issues. The Windows versions of iTunes was crappy. OS X releases that are now praised as "the best ever" etc, got tons of complaints for introducing bugs and instability. XCode has been historically crap (and it's much better now). And don't even get me started on the state of their Cloud offerings under Jobs.
Hardware wise the same. Every new release, from the original iPod to the iPad was met with complaints and bickering ("No wifi? Less space than a Nomad? Lame") -- even if it actually took wifi and batteries 5 more years to even start making practical sense to have on such a device for syncing. Aside from specs people complained about, there were also all kind of other HW issues, from the overheating G4 Cube, to the logic boards dying on G3 iBooks, to cooling goo spilling from G5 towers, the crappy "round" mouse, and lots of other stuff besides.
That said, I don't buy the "Apple software went downhill as of late" thing. First, because as said there were always issues. Second, because in normal use I don't see any particular decline. If anything things have got better, to the point where we complaint about trivial stuff. The thing is Apple of today puts out a heck of a lot more software and hardware products than the rosy Apple you remember.
I'd take iTunes in the back and kill it though -- as the latest redesigns are absolutely crap from a UX perspective. Then again, I wouldn't call that a programming quality issue -- more of a "idiotic focus and shoving on our faces of BS online music platform issue".
>Or, there's a chicken and egg question: XCode and the surrounding tools are atrociously buggy and hostile to the developer and it seems to increase with each release.
The opposite. XCode was "atrociously buggy" in the 3/4/5 era and before, and has gotten quite better in the 6/7 series (despite having to support a whole new language).
In fact a large list of early XCode 6 crashing bugs have been squashed months ago -- which was (as reported) around 90% of them.