When did World of Warcraft get ruined

It is said that World of Warcraft was ruined when the Burning Crusade was released, since many people thought that battlegrounds were downgraded due to the "Reinforcments" in Alterac Valley. Such games of AV would once last about a day, if not between 6 weeks and 3 months, as the longest told has been. It is also linked to many newbie players thinkign "Why the hell am I playing this?", and complaining to Blizz that they got