My version of QuickTime is called "QuickTime Player.app" That pretty strongly suggests that it is not an 'editor.'
Of course,
Mavericks and QuickTime Player as well as iMovie are three separate things. QuickTime Player nor iMovie are
not "
Mavericks." They simply are newer(?) versions of the same apps that were in earlier versions of the OS, many of which will still work in
Mavericks. I would hope that anyone upgrading any OS archive any of the apps that they like/used in the older OS before making the move. That's just normal procedure, IMHO. The old apps may not run in the new OS, but there may be changes in the new apps that you don't like or want or that change a workflow you are familiar with. But don't blame the OS for that, it's the changed apps that are the problem.
Sometimes the 'new' apps take advantage of new capabilities in the new OS, sometimes not, sometimes there are changes to your favorite apps, sometimes not. That's a lot of "sometimes!" That's why it's important to try out the new apps as soon as possible and why it's important to have the old versions archived.
I might add, it's also why it's important to check (all) the prefs in the new system and see what's available, changed, improved, etc.
Occasionally, the Help pages also have useful information... but they are not always updated as soon as possible/needed.
Details, details,
details...
Frankly, I've never found iMovie easy to use! I can remember that, at times, it could not even open a ".mov" file.
Or maybe it was a QuickTime file. Either way, it seemed incongruous and frustrating, at least to a noobie like me.