I don't like people who say WotLK sucked, because that's wrong in my opinion
WoW population increased ALOT during WotLK!
Source: http://wow.joystiq.com/tag/wow-population/
"Hater Argument:"
WotLK were that easy, even RPers and Casuals killed Lich King.
Five of WoW's best additions came during WotLK:
1. Hard Mode: Hard mode separates casual from hardcore.
In vanilla and TBC, there were no "real" hardmode with better gear as reward. The first trace of HM were: Zul'Gurub (Hakkar had special abilities if Panther boss were alive) Magtheridon (don't activate the cubes). But their real "Hard mode" were more difficult instances like Naxxramas (vanilla) and Sunwell Plateau.
In WotLK, blizzard wanted EVERYONE to be able to participate in all instances and making instead Hard Modes for hardcore raiders:
Ergo: Vanilla and TBC's "Hard modes" were more difficult instances, in WotLK, it was "Hard Mode" bosses, and your argument goes away.
Hardest boss in end game raiding in TBC were Kil'jaeden or Illidan. If you killed those, you defeated the last boss on the hardest difficulty. If you now kill LK 10 normal, you killed the hardest boss in the EASIEST difficulty, but if you kill him 25 HEROIC, you have actually accomplished the same as a TBC raider who killed Illidan/Kil'jaeden.
2. LFG Dungeon system is awesome!
3. Class Viablility. In TBC and Vanilla, all classes had their specific specc or they would suck!
Vanilla guy: "Hey, I'm a feral cat druid" "lol, specc resto or guild kick!!"
TBC guy: "Hey, I'm a elemental shaman" "lol go resto or reroll!!"
WotLK guy: "Hey I'm a Enhancement Shaman!" "Don't care, do DPS and don't fail and you're welcome to stay"
4. Vehicles. They can be boring or they can rock. IMO vehicles in quests are GREAT, it makes the questing more fun and entertaining. Vehicles in Boss fights/instance just sucks! I mean... Oculus? I didn't level up my char to 80 to sit on a dragon with 5 spells to kill a dragon (Eye of Eternity). I DID tho level my char to have fun, and vehicles + quest = YAY. The balloon quest in Gadgetzan rocks, the "kill that blue proto-drake quest" (can't remember name) in Dun Niffelem was awesome too! But probably not as a daily quest, you get tired pretty quick!
5. Ulduar. Do I need to say more?
But... In everythings that's good, is a bad thing. In this case it's the...
GEAR RESETS
A guy who started playing WoW during patch 3.3 NEVER had to go into Naxxramas, OS, EoE, Ulduar or probably not even Totc. Just go heroics and bam, you're done.
WotLK lasted very long time (over 2 years) and who haven't been tired of Dalaran, Argent Tournament, Icecrown Citadel, Northrend or anything like that? We felt that during TBC too! And a year after WotLK came out, we said "TBC WERE THE BEST!" but during TBC we said "VANILLA WERE THE BEST!"
In Cataclysm, we will probably say "WOTLK WERE BEST! Dalaran and ICC were so beautiful!! I miss the good ol' days! sadpanda"
So... When a guy says "WotLK sucked" I THINK they are very very tired of everything that you probably did everyday for almost 2 years.