It was one of the main reasons I quit playing. I never actually bought cataclysm, since most of the things that turned me off began in patch 4. The linear nature of the game was a major one though.
For me, I always liked the fact that the game was so open ended. You were always kinda steered to certain zones that were suitable for your level but there were usually a couple to choose from. And when you hit a new zone, there were normally plenty of quests to pick up which you could do in any order. And finding that odd, epically long quest line was always a delight.
Cataclysm took a good idea from wotlk (phasing) and over used it. Much as it did with cut scenes and a few other things. Phasing became over used. You'd enter a new zone and there would often be only one quest to do due to phasing. You would have to proceed though the whole zone in a particular area, otherwise you would simply have nothing to do.
Blizzard lost me because they became far too obsessed with the idea that everyone wanted to be in endgame. Everything about the game became calculated to steer players there. Increased experience gain. Dumbing down of levelling to the point where it was a bit of a joke. They didn't realise that for a lot of people, that is one of the most fun parts of the game. Not simply a means to an end.
I did a lot of raiding in wotlk but only because it was clear the devs were trying their utmost to steer people that way. Making raids more 'accessable' by making it so easy to get in to raids that there wasn't that much else to do. When I began playing wow during bc, I took a few months to get my first character to level 70. People were raiding black temple and sunwell before I set foot in karazhan but I was completely ok with that. I was in no rush to raid. By the end of wotlk and even more so in patch 4, it felt like everyone was being rushed to raids and everything else in the game was secondary to that. Almost seemes as though they might as well just let everyone start with level 85s with entry level gear since that's what the game seems to be all about.
I miss wow the way it used to be but I don't miss the game as I left it. I just hope the devs of my new favourite mmo that I won't name, don't make the same mistake since they've figured out how to make questing/levelling fun again rather than just a means to an end.