I think Come From Away has endured longer than other works related to 9/11 because it manages to tell a story of people impacted both directly and indirectly by the attack with just enough distance that it doesn't feel like you're wallowing in it. In a way, since the characters aee experiencing it from the outside, it's more relatable because that's how most of us witnessed the events of that day, too. Compare that to something like Paul Greengrass's United 93 which is masterful filmmaking, but so visceral and upsetting that many people refuse to watch it more than once.
It's also a welcome reminder of the best of humanity in the wake of the worst of humanity. It shows not just what did happen, but what might have happened too had different choices been made.
And it's just a damn fine show, too.