I always refuse to stand for an an anthem which calls upon a deity I don't believe in to 'save' a monarch whom I refuse to recognise. (I can't recall it forming part of my uni graduation ceremony 40 years ago. Perhaps Sheffield was more enlightened then than KCL is these days).
I don't think that any new anthem needs to specifically embrace multiculturalism; it simply needs to avoid anything which goes against it. It would also help if it was actually memorable. (How many people know the current anthem beyond the first verse, I wonder?).
Even better, it would help if there was general agreement as to exactly how many verses there were. (Some 'authoritative' sources say that there are officially only two verses in the current anthem, whereas the majority cite three, with others saying that there are four, five or even six).