9/11 was a one time thing. COVID is an ever evolving disease that was pretty lethal for certain groups of people, and bad shit for the rest. But a disease cannot keep living if it kills the host. Quarantines start, and the disease dies out. So naturally the less lethal evolution survives, because if it doesn't kill the host, quarantines are less necessary.
COVID is not over. It changed. As did we, by developing vaccines. But the urgency of quarantine because of over full hospitals are gone.
You can be cautious. And if you're in the risk groups you should. But societal necessity is over. Live your life, and stay at home when you have symptoms.