F1 survived before and after Senna and it survived before and after Schumacher. Same goes for NBA and even non-team based sports.
F1 will be more than fine after Lewis, especially now with Drive to Survive which took F1 to the next level. And from what I've seen of DTS it didn't focus too much on Lewis at all, maybe intentionally.
And while you're correct that Lewis brings in different demographics, there will also be plenty of people happy to see him leave Media will also be happy to see him leave so they can run new narratives, especially since they have couple of fresh faced British drivers they can push
They have Russell in a Mercedes, kids love Lando, Leclerc is in a Ferrari, Max as boring as he is has potential to break records.
Nah