When we rolled out IPv4 and started allocating IPv4 addresses to routers, switches, and PCs, we really did not take into consideration any hierarchy. We simply just assigned addresses as they came. That is why now our backbone routers are struggling to stay up and those routing tables are huge!
You can get this table at the following link for the latest updates: https://www.cidr-report.org/as2.0/#General_Status:
IPv6 was designed for efficiency, and even has built-in security, such as IPsec, for end-to-end security. But besides that, the protocols themselves have been trimmed down and are aligned for 64-bit processing, which will speed things up. If you look at the header of an IPv4 and IPv6 protocol, you will see how much smaller the IPv6 header is. Let's compare them in the following diagram:
IPv4 and IPv6 headers
As you can see...