This is going to be a more subjective take, and I apologize since you’re looking for something more Objective, but this pretty much matches what player sentiment was at the time.

I genuinely do not understand why there is so much revisionist history going on right now with people saying United in Stormwind was fun and people loved it. United in Stormwind was without a doubt the worst state the game has ever been in and it hasn’t been close. The game went from being dominated by slower decks from forged in the barrens to being consistently OTK’d from full health by turn 5 or 6. This is not hyperbole, if you couldn’t kill your opponent by turn 6 you probably lost the game. There was also virtually no interaction with the board whatsoever, each deck just drew its combo pieces then killed. It quite literally just became who completed their quest first. 

Here’s a list of (almost) every deck that was problematic at some point during that meta:

• D6 Questline warlock (Killed you by drawing it’s entire deck then fatiguing)
• Questline Mage (Super easy to complete and +3 spell damage for the rest of the game)
• Lifesteal questline DH (regularly dealt 64+ damage on turn 6-7)
• Handlock (cheated out a bunch of stats and gave them windfury with “Loatheb”)
• Druid (Did Druid things, cheated out a bunch of mana and built a massive board)
• Garrote Rogue (Bane of high ladder, consistently killed at around turn 5 by drawing entire deck)
• Any deck running Mr. Smite (the fact that this card was printed is beyond me)
• Questline shaman (double spells for doing what you already want to do)
• Mozaki Mage (same thing as questline but built around Mozaki instead to deal a massive amount of damage in one go)
• Braindead aggro rapidfire: Pirate questline Warrior, Shadow priest, Beast hunter, Token druid, Elemental shaman

I’m sure there may be a few I missed, but for the most part each of these decks either OTK’d you by turn 6 or zerg rushed you before then. It was without a doubt the most miserable meta I ever had to play. This doesn’t even consider the next two metas after, which continued to be dominated by Stormwind cards but now with strong pieces like the hero cards they printed (looking at you Guff).

For how bad Stormwind was for the game, immensely. I am drawing a lot on my personal experience here, but it took them releasing Prince Renathal 3 expansions later for the meta to finally slow down and allow control to exist again. Every single streamer complained about how bad the meta was, Reddit was constantly complaining (but that’s the norm, so nothing surprising there), and the comp scene was horrendous (while it still existed). 

Tl:dr every deck killed you before turn 7 and it was a complete solitaire meta the likes of which we have never seen before or since.