Can you elaborate on the issues with iTunes, Wifi, and Xcode? I know the app store is just a wrapper (which makes it pretty bad) but Xcode is a wonderful (but buggy) IDE, I don't understand how you can make WiFi bad, and I really have no idea where they went wrong with iTunes.
iTunes is a slow, bloated mess with UI that gets worse with every release. Classic dumbness: Adding 1 song or photo to a phone requires erasing the entire phone because it's synced from another computer? Or trying to sync a folder of photos from computer -> brand new iPhone with brand new iTunes doesn't work. Just stalled progress bar forever.
WiFi: There are constantly WiFI problems with OSX and iOS. From plain-ol' reliability to straight up bugs. This isn't including boring DNS stupidity from OSX.
To be fair, in the time of RealPlayer and such, QuickTime was the least bloated and best performing video player around. There really isn't a use for it in 2016, though.
There is a certain irony that after all the arguments about how plugins are bad and we must kill Flash, actually video on iOS devices typically still plays via a plugin today, just a different one. Moreover, because of Apple’s policy about browsers all having to use the same engine on those devices, no-one can provide an alternative browser that does better.
This situation breaks everything from basic cookie mechanics to possibilities for caching short videos for offline use, which should have been letting us do all kinds of interesting and useful things now that the videos are supposed to be part of the normal content on a page.
Apple not supporting Flash was a crucial part of it's demise, though. Without that, we might be running Flash on mobile today, even though it was terrible.
They did actually support it for a while on Android, but Apple never wanted to support third party browser plugins on iOS, and since the Android port was horribly slow even on the most basic swfs and was a huge hack, Adobe decided to drop it. AIR is still supported on both platforms, though (and I hear it's quite good).
Flash wasn't even supported on iOS. I'd argue that was huge in killing off Flash, since anybody who wanted to make their site work on mobile could no longer use Flash.