My gut reaction: There's no company the size of Uber that could die more quietly. The world's reaction would be a muffled "meh".
Uber doesn't even own their most important asset, which is their drivers, and if they collapse catastrophically their drivers will simply turn off the Uber app and download one of a half dozen competitors' apps (if they don't already have it). For Uber customers, the transition will be even easier.
Maybe I'm missing something: This isn't like a car company that owns and manages factories, or like a tech company that has labs or does significant R&D, or even a bank that has lots of employees and owns other assets.
So genuine question: what do we loose if Uber vanishes tomorrow?
(Don't get me wrong, I'd be sympathetic to their employees who need to find new jobs, but my guess is that their skills are in relatively high demand.)