Fragmentation is mostly removed on IPv4 as well. Almost everything sends DF, and there's very little legitimate fragmented traffic. You can just drop fragments wherever convenient. If you want to be nice, it's a good idea to have a small reassembly buffer, but if it's too much work, just drop them.

It's beyond too late to change anything, but I imagine if IPv6 had started with a sensible rollout plan and worked backward from there, it would look somewhat different and it would have taken a lot less time to take hold.