On a statistical level, the vaccines don't have to be 100% effective, and they aren't. For every person you hear about being sick after 3 doses, there are probably 10 people that would have gotten it, but didn't. If there was 10x less healthcare capacity, you can see why that would be a larger problem.

That said, the vaccines do seem pretty focused on the 2019 variant of COVID-19. It's 2022 now, and that variant is dead. So we're definitely getting imperfect protection. (I got my 3rd dose anyway, of course. And I'm still treating the pandemic like a pandemic. I skipped holiday travel, I don't go out unless absolutely necessary, etc.)