In the real world, people who design and operate large networks are the very same people who staffed the working groups who designed IPv6. It's their design.
A key aspect of IPv6 is that the address space is big enough that 'carving it up' for subnets is dramatically simpler even at the largest scales. You don't need to be frugal with network sizes, and you don't need central coordination to avoid conflicts. This is huge!
E.g.: If I want to deploy a cloud VPC (or vNET), then I have to go find "the guy with the spreadsheet" and peel off a tiny(!) private IPv4 address space. If he's away from his desk or on holidays, my 1-minute automation script will now take 1-10 working days until he's back and responding to requests. With IPv6 this just disappears as a bottleneck.
Half the US has already deployed it and 100% of the mobile carriers. I would say the detractors who continue to stomp their feet about not deploying IPv6 are holding a fake title of "Network Engineer". People need to grow up and do their job or get out.
In the real world, people who design and operate large networks are the very same people who staffed the working groups who designed IPv6. It's their design.