Not good enough. You're not thinking through the fundamental parts of a story. It's not good enough just for the antagonist to fail. He has to fail for a meaningful reason (assuming the central conflict is between the protagonist and antagonist.)
Here, watch me write the ending to pretty much any science fiction or fantasy story every written in 20 seconds. "The good guys find a technology/magic artifact that kills the antagonist/creates an army for the good guys/solves all our problems.
We find a technology that makes the Death Star go boom without having to fight it! We find a magic artifact that makes the evil demon shivel up and die! We find a magic artifact that summons up an army to kill all the evil orcs and goblins.
Are these good endings because the antagonist fails? Do these endings offer a 'sense of achievement' because the antagonist fails?
No. They're ridiculous. Because they fail to follow through on the basic principles of a story. Just like Inquisition does by having the bad guy be defeated by being being whacked with a sword for five minutes without any complications or struggle.
He does fail for a meaningful reason: his hubris in attempting to claim godhood, which was the source of his downfall the first time, once again creates a world and hero who opposes and shatters every value he holds dear. Corypheus has three sources of power: the foci he stole from Solas, the army he acquired on his purported divinity, and his dragon. His plot is to assault the black city by claiming the anchor and shattering the chantry that supplanted his beloved Tevinter. Yet in his hubris, he creates the instrument of his downfall.
Rather than strike you down himself he orders his mooks to do it. He loses the orb, and you claim the anchor. Over the course of the game you claim its power. You shatter his purported illusion of divinity and restore the institution he sought to break. You create a counter part to every source of his power: you use the Well to obtain a counter-dragon, use the other side of the Red Templars/Venatori to found the Inquisition, and Master the Foci using the Anchor to heal the heavens he sought to break. The tide of power literally shifts from him to you by the endgame. Where at the start you were no one and alone, at the end Corypheus is nothing and alone. That's pure theme and it's what makes the fight dull. Gameplay is sacrificed for theme, not the other way around.
Corypheus sought to become a god to give purpose to a world he saw as broken. You rise from the literal ashes of a broken world to give it renewed hope and a symbol in the Inquisition.
Just look at the symmetry between the start of the story (told via flashback) and the end. The breach is created when Corypheus drops the orb without completing his ritual. The breach is closed when you use the anchor to *rip* the foci from his hands at the height of his physical power. You've reversed your roles entirely.
You restore the Chantry where he sought to break it. You eschewed godhood where he sought to claim it. You healed the heavens were he sought to assault them. You are in the most literal and thematic sense his antagonist.
I just cannot wrap my head around how you think DAI is thematically empty at the ending.