Which also happens to be around the time a lot of people would have had their 2nd or 3rd shot, imagine that.This has already been explained You will notice the deaths levelled out at the exact same time Omicron became the dominant strain. Not when the vaccines were introduced.
People we being offered boosters at the stage you are pointing out because they weren't working as well as expected.
At least you now seem to be acknowledging the reality that the death rate is less though, and we can put your "The death rate hasn't decreased by any discernable amount" statement to bed.