@ArdeaCinerea
The WHO is not so much predicting as warning that this is what can happen and health systems may be overwhelmed. This is more clear from the full statement posted by a pp, where recommended action is also outlined.
I remember early on in the pandemic a lot of people were already saying that everyone in the world will be infected and we need to make peace with that. This kind of self-fulfilling prophecy and defeatism has guided policy, unfortunately. The vaccines were highly effective at preventing infection and transmission with the earlier variants, so if wealthier countries had made a massive concentrated effort early on to help vaccinate the world, prioritised this over anything else (why were there not 24/7 vax centers everywhere?), and kept borders closed in the meantime, we could've perhaps had a better outcome than "repeated infections for everyone and a shittier life for vulnerable people, forever".
The vaccines were highly effective at preventing infection and transmission with the earlier variants
Were they really though or would their protection have waned over time regardless of different variants?
Plus I don't know how realistic it is to vaccinate against a coronavirus (something that has certainly never been achieved before) because they simply mutate too quickly.
The only way to achieve what you suggest would have been to vaccinate the entire world population at the same time with sterilizing vaccines. That is, to do something impossible as we have neither the logistics nor the (sterilizing) vaccine nor the will of everyone to be vaccinated nor the individual need.
There are scientists who have been voicing concern for some time now that mass vaccination, with non sterilizing vaccines, during a pandemic, against a type of virus known to mutate quickly, would result in the emergence of a highly infectious vaccine resistant strain.
Which may well be what we are seeing Omicron. We will know more over the coming weeks I imagine.