Its arguable. If you compare QF to SQ then yes they have a much older fleet. But if you compare QF to the US legacy airlines or EU, it's more or less about on par with them give or take a couple of years.
The 330 frame itself is ok. It slots in at about #4 at the moment (especially out back) behind 350/380/787 for me.
In all honesty the cabin is almost always the bigger factor than the actual plane. We'll see once the refurbishment is done if the average pax can even tell they're on an older 330.