To me, it was when Cata came out, It was a decent expansion but, In my opinion, WotLK was the peak.
I can’t put my finger on it, or point out anything specific, so I’ve asked in game. No one could give a specific reason either, however, I was surprised to hear that some people felt WotLK was the start of WoW’s downhill trend.
Can anyone share there opinion where you feel WoW lost it’s lust and why?
I agree with you. For me TBC and Wrath were almost as good as Vanilla. Some minor things bothered me, but the downfall was Cata.
For me it has nothing whatsoever to do with dungeons and raids - it’s the world and the “feeling” of this. Until Cata the world was big, dangerous, your choices held significance, even a small plus to your stats (buffs from co-players or cooking) could mean the difference between life and dead.
But in Cata the starting zones no longer held “red” mobs, Questing turned linear and hand-holding, Talents became spec-based boxes … all the flavour items disappeared and levelling became so inanely easy that you could take on 10 mobs 2 or 3 levels over, and never die.
The world died.
The game became potato easy
Cash shops
No world pvp
Hamster wheel buff/nerf strategy to keep you guys re rolling fotm.
Do i need to keep going? Retail is a literal cartoon now
TBC.
When gdkps started 
You’re going to get two primary answers:
Wrath, due to RDF and the idea that the game peaked at that time.
Cata, due to Raid Finder, the destruction of the original Vanilla content and other retailesque changes.
A minority might say TBC because of flying mounts and leaving Azeroth.
Personally, I agree with the Cata people. RDF was a fantastic addition because it got people running dungeons again. Of course, the Arthas lore is peak Warcraft for me, too. Cata just changed too much stuff.
WoW started its decline in new subscribers and in bad game design when Wrath launched.
Subscriber Stagnation
It was the first expansion that was not reliably growing WoW’s subscriber counts, only replacing sub losses at a 1 to 1 ratio, with a small bump when the ICC patch released due to Arthas’ massive popularity. This means that Wrath was dissuading just as many players as it was persuading, which caused the stagnation visible on the popular subscriber graph.
“The Merge”
Activision and Vivendi Games merged to form Activision Blizzard in July 2008, just a few months before Wrath. This needs no explanation. We all painfully know this story. The base work for Wrath was not terribly influenced by this event, but all of the decisions following absolutely were.
Bring the player, not the class
Wrath was the expansion where Greg Street introduced “Bring the player, not the class” as the over-arching philosophy of raid design. This was the beginning of the mass homogenization seen in WoW’s class design to this day. This resulted in a loss of class identity, where the only identities players could hold on to from this point forward were raw number output, and the graphical representation of their class on screen. The effects in arena were similar, causing a lot of arena play to feel dull.
Heroic raids
Many other retail-esque systems were introduced in Wrath as well. We saw the first raid difficulty difficulty setting which ballooned into the Mythic system known today.
Heroic raids, continued…
Raid difficulty in terms of mechanics took a massive upswing after the introduction of difficulty settings, giving us extremely difficult Mythic raids which many see as being a product of retail. While I personally do enjoy a good challenge, I can still fully admit this kind of game play is a retail feature.
Microtransations
The beginning of microtransaction bloat began in Wrath (no, the sparkle pony did not outsell the entirety of Starcraft 2, that was poorly interpreted data) which resulted in the justification for the game to contain an ungodly number of mounts and pets. Someone recently told me there’s over 3,000 mounts in the game at this point in time. I can’t imagine caring about seeing any mount in retail at this point.
LFD, RDF, LFR
Looking for Dungeon and Random Dungeon Finder were introduced in Wrath, which eliminated any social aspect of formulating a group and also eliminated any open world requirement to travel to your dungeon. This later blew up into the deeply unpopular Looking for Raid apparatus, which is a hallmark of what people believe “retail” to be.
Achievements
Achievements were introduced in Wrath, which brought about a massive growth (I say bloat, due to the number of junk achievements) to the amount of instrumental play available in Wrath, which some criticize and being contrary to the spirit of an open world MMO. Instrumental play is defined as a type of game play that’s driven by explicitly listed goals to achieve, rather than choosing your own activities and adventures which is a hallmark of “Classic”
I’m sure there are more features I’m forgetting about, but this is pretty much the gist of it.
Post-Wrath
Later, you had even more egregious examples in the form of transmog, the destruction of Azeroth, and the Disney-fication of character models and animations, but for the most part, the retail ball got rolling with the launch of Wrath.
You still want some pve gear on most, if not all, classes in tbc for pvp so that isnt entirely true. Maybe not as much as classic though.
Give us a TBC core with the level cap set to 60 and close the Dark Portal.
Raids can be tweaked to increase difficulty to make up for the increase in player damage output due to talent trees not being stupid. Implement SoD-ish updates to tier gear.
The first time I walked out of Ironforge. All the way down that big hill.
Cross realm zones in Cata. Blizzard demonstrated that they thought realm identity and community no longer mattered.
MoP oddly enough. for me anyway.
Cata was great. Classic + …almost
TBC was when it started slowly rolling downhill
then total crash with wrath 
TBC was better than vanilla. Vanilla you just raid log to bis. TBC has things to do in the world. If you’re for some reason not raid logging on vanilla it’s because ur not good at the game unfortunately.
Cata is when the art got fat and chunky, and they quickly moved towards this cutesy disney/cartoony style art. It also started to get overly goofy, and it lost so much of the sharpness to the world, the original gritty world went with it.
I hope with the research they found with Classic and what made it so good, they will be able to balance going forward.
For me it was Legion. Sure, cata changed a lot of things… but Legion is when this game started to feel like an entirety different game rather than an expansion. “WoW 2” if you will. I think it was the new “Disneyfied” character models and animations changes that completely killed it for me, personally. The engine and UI felt different after that too… idk why but it reminds me more of GW2 now.
I’m surprised I scrolled through the thread and made it all the way through without someone mentioning WoD. I think that was truly the beginning of the end.
I think thats fair. I see Legion as the “end” of WoW as it feels like WoW 2 at that point and an entirely different game. But i think you’re right that WoD was the beginning of that end and what ultimately led to Legion and beyond.
WoD was a ‘placeholder expansion’ in many ways, people tend to forget about it. It had many bad things, but some fun ones too, that ever got unfolded
lol I think they tend to forget because a lot of people stopped playing in WoD.
WoD was the genesis of so many bad systems. The biggest mic drop? Blizzard stopped releasing sub numbers BECAUSE of how bad WoD was. That should tell you all you need to know.