I and my guild did the full vanilla progression starting at day 1. When 1.12 came out, everyone was just playing ALTs gearing new chars for TBC, the things you do at the next expansion patch.
It was the shit patch nobody cared about, some people geared alts while others took a break till TBC. Nobody cared at 1.12 for the game since it was made for the wide mass of players. The exploits in pvp made it unbearable even if you did not raid.
Many TBC babys started at 1.12 or at the end of it and its pretty sad to know thats all they saw from vanilla. LFR-raids and 2 weeks to R14 cheat shit. It was not a good time in WoW and its funny as hell that Classic got this version of the game.
In the end the success of classic means just the blizzard was right since years, people want easy LFR mode.