Screamo is emotional post-hardcore music. It is not pretentious, only the people involved can make it that way. It is not a trend, only the people involved can make it that way.
Note : Just because you heard The Used and Finch and thought they were screamo doesn't make them the first ones to do it, and doesn't make it screamo. They are very far from it. I doubt you'll hear Hot Cross or Yaphet Kotto on the radio anytime soon - and that's just the way we like it.
Saetia, Hot Cross, Yaphet Kotto, The Assistant, Neil Perry, You and I, Off Minor, Kaospilot, Racebannon, The Kodan Armada, Circle Takes the Square, Orchid, pg.99, City of Caterpillar, Usurp Synapse, An Albatross, Bear vs. Shark, Since by Man, Transistor Transistor, and plenty more.