Ok...the title is an exageration of sort. Not all developers are inept. Some produce very good products.
But it seems Apple is frantically writing new software to fill in holes left by developers. Apple has left developers a lot of time for them to write good apps but I think Apple got tired of waiting and wrote their own.
All the browsers on Mac had a share of problems (yes, even Chimera believe it or not...probably the browser with the most problems, IMO, even if it's crazy fast). So Apple wrote their solution...and it seems to be a success.
Lets face it...there was no good presentation app on Mac. Anyone could have written a nice presentation app that used Quartz...but no...it didn't happen. Apple wrote their own. PowerPoint? Puhleaze!
iCal, iChat? I think iChat was to fill in the 'easy-to-use and bloat-free IM app' category which was non-existant until Apple wrote it. iCal was written probably because there was no good calendaring app except for maybe Entourage which was part of a ridiculously expensive $400+ package up until only recently (And Windows user say we're crazy for buying expensive Macs.

)
iMovie and iDVD...no app even come close to this...again, Apple pioneered this category on Mac.
I mean c'mon! Apple left doors wide open...but they can't leave the doors wide open forever. I'm glad Apple is providing the missing software! Apple seriously deserves a pat on the back.
DVD Player provided by Apple is cool but it's somewhat lacking (Apple leaving the door open?) I have yet to see anyone work on a good DVD Player with 5.1 support or 7.1 support (now that cards are out for this.) VLC is ok but the interface is really bad.
It's only a matter of time until DVD Player is updated and close doors for developers trying to create a good DVD player.
You rock, Apple!