this is a simple reason
You're missing a big bunch. Here is what it is, by example.
A healthy person might never know that he has a liver problem until he falls over because of it. A person's liver can be up to 2/3 ravaged by disease, but if the other 1/3 is reasonably healthy, nobody will know it.
Same with the cells in the body. The cells are damaged, but people don't know it because they are still working quite well.
It is the job of certain viruses - the Coronavirus family of viruses included - to attempt to repair certain kinds of damage to cells. The viruses are damage specific. In other words, if a certain kind of damage is repaired by the immune system, the particular virus that was working on that particular kind of damage will go away.
People are sick in their cells. It is a kind of sickness that doesn't hinder them from everyday life. Covid is simply attacking the sickness that is already there. But because the sickness is so deep, and because the Covid virus doesn't recognize that fixing the cells is ultimately worse for the person than letting the person heal slowly, Covid jumps in to do its repair work. The person gets sick, maybe dies, from the shock of repair work being done too rapidly and extensively by the Covid virus.
Medicine and modern vaccines - pure poison - simply change the nature of the cells so that Covid, which is damage specific, can't find its kind of damage any longer. So, the medicine works to stop Covid.
But the medicine destroys the cells in other ways, and opens them up to "attack" by other viruses trying to fix other aspects of cellular damage.
The thing people should be doing is staying away from poisons, getting proper nutrition, getting sunshine and exercise, and hugging and kissing other people to get herd immunity from thousands of viruses.
It's no wonder that Gates says that we haven't seen anything yet. Our cells are so weak from not maintaining proper health, that any number of viruses could attack and make us us sick... any number... like thousands or millions.