Why not? I did DOH-AKL in Y recently and found it absolutely fine. I quite enjoyed it actually, wouldn't have any qualms about doing such a long route again. Planning on doing it again next year.
You can easily keep yourself active in a Y class seat, move around now and again, even moving your ankles and knees every so often is enough to keep DVT at bay. Flight socks are provided in many amenity kits too.
If you don't want a 17 hour flight then don't book it, but many people will see no problem at all in doing so.