Lol, you are saying that an established thing is DEM, and something that came out of no where is not. What a joke. It´s you who is showing cognitive dissonance, but whatever.
I promised myself I wouldn't do this, but what the fuck.
You are completely missing the point of a DEM. Urahara being "established" is absolutely fucking irrelevant, no matter how many times you self-satisfyingly bring it up. A character known for solving problems by appearing out of the blue with a panacea is a walking-talking DEM no matter
how many times he does it. Imagine a manga where
literal God shows up at the climaxes of arcs and undoes everyone's problems. Maybe you see a panel of him halfway through each arc saying "hm, I'll look into this," then everyone gets fucked up and they're all about to lose, and he shows up and says "hey dudes, here, let me undo whatever your problem is." You'd come to expect it over time because it keeps happening, but any coherent storytelling involves struggling and overcoming problems, not having them negated by a higher power. You might expect it as a reader, but the
plot doesn't expect it. Those half-dead shinigami sure weren't expecting it. A story is written to convey the overcoming of obstacles, and when they are abruptly
negated instead of overcome, the plot has been affected by a DEM.
Let's paste your definition again:
a seemingly unsolvable problem is suddenly and abruptly resolved by the contrived and unexpected intervention of some new event, character, ability, or object
Note the OR in that sentence. No, Urahara is not unexpected or new. He was hinted at working on something, on figuring out the situation, on maybe formulating a strategy. But the
object he brought with him is both unexpected and new. That object's
ability is both unexpected and new, even if an explanation for why it works establishes a connection to previous events after the fact. Arguably (but I won't argue it since I know your retort) the teleporting of the pills is unexpected or new. I'd personally say that him providing a
pill instead of a
strategy was unexpected. And more than anything, his arrival at the exact moment Hitsugaya was about to lose was both contrived and unexpected. This is more than enough to qualify. As generally the
bearer of "some unexpected or new ability and/or object," I'd say that he inherits the DEM for himself. "Whoop, Urahara's here, time for him to DEM the situation into oblivion." It's almost his defining character trait.
You can't just say that because someone DEM's all the time, he's not a DEM.
AND, as for Blackbeard in One Piece, that's not a DEM because it didn't
resolve anything. Yes, it was unexpected and new, but you are missing the most important element of a DEM. It's the resolution. Blackbeard getting that fruit didn't change the war, Shanks was like "get outta here you dick" and Blackbeard left. Hell, Shanks' arrival was closer to a DEM than anything.