Exactly. I also quit when cata came out (well actually between the sundering and cata). Our guild disbanded at the same time since the majority of our guild's leadership were quitting. It was a levelling guild and levelling has become so easy that the guild was pretty redundant - and no longer much fun in the opinion of many guildies. Pretty much a race to get to max level that should be as quick as possible in the opinion of the developers. A means to an end rather than an enjoyable part of the game in itself.

For me the most fun part of the game was always exploring and levelling. Now levelling is a joke. I used to think twice about taking on more than a couple of mobs at a time while levelling a toon. Now you can take on 6-7 without breaking a sweat, and that's after removing heirloom gear. I levelled a new toon to level 70 in a few days and only died once. Ludicrous. You don't want it to be too hard but you want it to be at least challenging enough to hold interest. With all the over-use of phasing there's no longer any sense of being able to explore and area and do quests at your leisure. You go in to a new zone and there's only 1 or 2 quests available. You're pretty much hand held through the zone since you can only do most quests in a certain order and progress in an area in a certain order. Sure the new quests are innovative in many ways and certainly entertaining, but if I want passive entertainment that requires little effort I'll watch a movie. Not invest hours in a game. I guess the game's largely been ruined by so many players expecting everything now. Easy epics. Easy achievements. Easy vanity rewards. I never used to expect the same rewards that the top raiding guilds got.

It seems the only part of the game that's still challenging is pvp which I only ever did casually, and raiding which I also only ever did casually (and even raiding/heroics are pretty much facerolls unless you're doing hardmodes.