QuickTime should start supporting more formats, not fewer!
What a strange omission. You would think QuickTime is extensible enough that they could include a MIDI component in the latest release. It's not like a MIDI wavetable eats up a ton of space.
They're really working backwards from where they should be going; I use VLC almost exclusively for video playback because QuickTime has such weak format support, where VLC can play just about anything. Heck, my original Xbox running an old version of XBMC can play far more formats than QuickTime! 😛
Fortunately, I had QuickTime 7 installed because I always install any "old" software whenever Apple makes it available as an optional component. Otherwise you're left without vital tools like Rosetta and older Mac OS X (10.3/10.4) development targets in Xcode.