Wealthy countries have way more old people, and way more vaccines. COVID is still more dangerous to elderly vaccinated people than to unvaccinated teenagers.
You can sometimes even see this effect in one country, if all the old people are vaccinated and none of the young people are, you'll still probably get more COVID deaths per old person. If you just look at mortality by vaccination status you'll see lots more COVID deaths in the vaccinated cohort, but that's because the vaccinated cohort is just old.
Probably because while it's a simple observation, it's not an intuitive one, so a lot of us had to have it pointed out recently. It's the nature of the math, not anything that has to do with covid or can be sensibly argued with.
You can sometimes even see this effect in one country, if all the old people are vaccinated and none of the young people are, you'll still probably get more COVID deaths per old person. If you just look at mortality by vaccination status you'll see lots more COVID deaths in the vaccinated cohort, but that's because the vaccinated cohort is just old.