Cataclysm revamped the entire landscape of Kalimdor and Eastern Kingdoms, changing most if not all of the quests there too and giving no ability to run the old-school environment and quests outside of Classic. It introduced LFR, which if you were a raider (not that I was ever a major one) was the death knell for how raiding was to be in the future as now every chromosome-hoarding player could run instances at less difficulty than 10 man normal. It also began the start of, as far as I know, the dumbing down of the game as stats for basic attack and defense (attack/spell power, armor penetration; block value and defense), as well as weapon skills in general, being neutered severely or axed entirely.
It was the last expansion to have actual talent trees, but they were changed heavily in Cataclysm with the total talent points being reduced from 71 to 41 and specific specializations for said talent trees, limiting any cross-tree combinations (which tended to be shit most of the time
) until 31/41 points were spent in a single tree. Archaeology, introduced in this expansion also, was a complete slog. Couple that with the ability to get actually-useful items from archaeology, and you can see the issue.
Though, looking back on it, I may be a bit too harsh due to the nostalgia of WotLK and the massive shift from that to Cataclysm.
