I've seen estimates of herd "immunity" at being around 70%, but our kids are not yet vaccinated. They also are experiencing more infections how than before perhaps because of that, in part.
If an infectious person passes it on to say three people on average, and two are vaccinated or otherwise resistant, they might now pass it on to only one person, which would be steady state, R naught at unity. You reach the point where infected people don't pass it on to anyone, and then it largely subsides, variants aside.
This one was bad because so many were asymptomatic for fairly long periods of time. I think the flu gets you sick about the time it becomes infectious.