Nah, thats just one of many many reasons, no one single thing killed UT3, it was many things, big and small, that all stacked togeather makes for one huge turnoff for the vast majority of people out there, the game itself, its launch and how Epic has handled it post release has just been full of flaws.
Seriously, point to any aspect of UT3 and how it has been handled, and you find flaws and shortcommings, even the one thing it does well, its core gameplay, has its flaws and bugs.. no game is perfect, but there's a limit to how many problems we'll forgive and put up with.