I agree that talking about currencies now is like talking about matching the thread color of the uphostery on the chairs on the Titanic. Charms are nowhere near the issue. It’s just a distraction, and we should ignore it.
I think that pet dungeons may have been what damaged pet activity, and the way devs perceived pet battles.
The devs have dungeons on the brain. It’s in their DNA. But Pet Dungeons were not a success. They were not a total failure, but they did not increase activity, which is what they needed to do to be counted as a success.
Whether you look at Wowhead or DfA, only about half of the people doing WQs regularly completed the dungeons, even once. And the dungeons were designed to become obsolete soon after their launch.
So I think the devs, whose brains are awash in Dungeon neurotransmitters, threw up their arms in despair and said “If even dungeons don’t work, then nothing is going to work.”
But I think Dungeons were never going to work, never could work, and were a bad idea in the first place, [ * ] at least if what they wanted to do was increase pet battling activity. And they should have abandoned Dungeons sooner and tried something else. But Blizzard devs are known for their unwillingness to make conceptual changes. (Tactical and mechanical changes, yes - they can be very agile and responsive on those when their attention is on them. But not so much broad conceptual admissions.) They would much rather abandon than iterate. [*]
But the devs are looking at it and saying “Look how much work we put into it, and the players aren’t responding. Pet Battles must be unsustainable.”
Now, I’m sure that isn’t the only factor in this decision, but I suspect it is probably one of them.
Your “no new content” ide is right, I think, but dungeons wasn’t it.
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[*] I could write an essay on these topics!