Personally, though I might be wrong, I'm of the opinion that at least as far as existing variants go in the UK most of the people more generally likely to die from COVID already have, there will still be some older and vulnerable, etc. who are protected by the vaccines.
Additionally oddly Omicron seems to be skewed towards the older population, even more so than older variants - not just that there was a shift away from the lower respiratory tract, which was one of the things which made COVID relatively more deadly across the population broadly, the chances of death seems to be slightly higher for the very elderly with Omicron than older variants which I wouldn't have expected - lung inflammation and all the problems which go along with that such as potential for pneumonia is especially nasty for older people.
EDIT: Though maybe it is the fatigue which is getting them - Omicron seems to come with milder, but longer lasting, fatigue which might be less of an issue for younger healthy people but grind down the ability of very old people to recover.