ZG was a catchup raid for guilds that could not gather 40 raiders just yet, and wanted to start gearing up.
I remember it to be quite challenging back then, particularly Jin'do and Hakkar which took a while to down.
But back then, no one had gear from MC and BWL. Everyone was pretty much fresh 60s. Also, the knowledge of classes and the BiS list was not as common as it is now, and people had little experience with raids and addons.
People are saying ZG was between MC and BWL, but that's because the gear is much better itemized. The developpers had also learned a lot.