Rose coloured glasses off people. Things were just as bad coming to the end of Vanilla as it is now.
The reason why things were like a field of flowers back in Vanilla was BECAUSE it was new. There were no sites telling you what gear was best, what spec was best, rotation, etc. It was still a learning experience.
Yet despite this there were expected roles. Warriors were tanks.
Paladins, Druids, Priests and Shamans were healers.
The rest were dps.
I'm sure we've all met a guy who was bad, but a nice guy. And we felt sorry for him. Some can be helped, some can't. UNfortunately based on the reaction from his server he'd been doing things wrongly for so long that no one was willing to give him another chance. This is the server's fault in part, but also his own. It doesn't take long to look up a few details on your class, ESPECIALLY if you're doing less dps than the tank.