You make some good points but there's one thing I think is going on and is worth pointing out.
Apple is in an interesting spot at the moment in that, due to the sheer popularity of just about everything they make, they're selling more Macs now than ever before. People are switching to Macs more now than ever did during that "I'm a Mac" campaign. It's anecdotal evidence, sure, but my wife switched to OS X from Windows and didn't lose any momentum.
The issue Apple faces is that they've always had this small but devoted group of people to sell to. They could get away with software being done the way it was and at the quality level it was because they knew their core contingent would lap it up. And they did. But it likely left them with software that was difficult to maintain and lacking in features which would be difficult to add to the existing code.
Take Microsoft, for instance. By all accounts, the source code for the Office products is a fucking nightmare for a lot of reasons, not the least of which is the need to maintain compatibility with all of the documents already out there (and we know they don't always get that right either). The story goes that a several years ago they tried to rewrite everything from scratch while maintaining compatibility with existing documents. It was called Project Pyramid or Triangle or something. It was a disaster and after years of work and millions of dollars it was canceled. Fortunately they had continued to work on the regular Office suite so they still had something to ship (no Netscape level mistake made) but they simply had too much code in use by too many people to merit changing it. Look what happened when they tried to redo large portions of Windows - Vista was the result and it was a disaster that's kept a lot of the world on XP to this day.
Apple has their iWork suite and they realized with as many people getting Macs these days, and with Microsoft for a long time refusing to upgrade Office for Mac, if they were ever going to redo the code base now would be the time. Now, before millions more people use it and maybe make it part of their workflow. Same as Final Cut Pro. Thing is they don't know which features are really being used and which ones aren't so they come out with basic versions missing those features and when people complain that Thing X is missing, they put it back in.
It's true that the killing of Apeture is becaue they're not interested in the pseudo-pro photogtapher scene but I think that their other recent maneuvers with software are because if they want code that is long term maintainable, now would be the time to do it, before tons of other people use it and then they're stuck.
As for the DJ's and the cables, I would think anyone who wants to use a Mac professionally would know to get something other than the new MB. Its likely neither the most durable or portable Mac (11" MBA probably has it beat on portability) but its worth noting that if you have AppleCare (yes, an added expense) they'll replace broken cables for free just by bringing them to the store. Not an option if there's not an Apple store in the area but as a counter point to the "they make the cables crap so you have to buy new ones" argument, they'll replace your worn out cables for free under AppleCare.