IPv6 addresses are so long that you can't remember them long enough to read the address from one machine and type it into another.
Which is not a problem because normal people don't have to read the IP address from one machine and type it into another. They use DNS and DHCP, which were specifically intended to eliminate the overwhelming majority of instances of dealing with IP addresses directly.
I've been a networking software engineer for most of my career, so I do have to deal directly with IP address (v4 and v6) routinely, and I don't complain about it. My mother is not a networking software engineer or IT person, so she's had to do that exactly ZERO times in the 15+ years that she's used the Internet.
But, it seems unworkable from a human perspective. No I haven't thought of a better solution. I'm just saying that this is a significant usability problem and a barrier to adoption.
It's not a usability problem, because people shouldn't be directly dealing with IP addresses. If people are directly dealing with IP addresses, that is the usability problem which needs fixing, and not the length of the address.