You are being condescending based on the type of content that other people care about. Maybe this will help you better understand: consider HN starts banning your comments and someone chimes in, "oh dear, how will yters survive without being able to post his naive opinion?". Hope that helps.
For some of them, it is part of their vocation, and so they'll have to survive by re-training, changing markets, or else they might not survive.
The question is how Tumblr will survive without users.
Tumblr won't survive without users. But the users will survive just fine without Tumblr. They'll find somewhere else or make somewhere else.