The demise of Klaine had the best build-up and the best individual ideas. Since they’ve both been at the forefront of Season 4, we’ve seen Kurt and Blaine slowly drifting apart, and everything fell into place for a moving and honest break-up story. Blaine channeling all the conflicted emotions of cheating on someone you love into his “Teenage Dream” reprise was a poignant concept, moderately well executed. It was also smart to acknowledge that Blaine had been tempted before (by Sebastian) but it took crippling loneliness, not just lust, to make him unfaithful. And Chris Colfer’s portrayal of Kurt’s anger, betrayal, guilt and sadness stood out even in a generally well acted episode.
So why did this split feel so calculated? Aside from how ridiculous it was to see Kurt manning Isabelle’s phones (he couldn’t be busy in other ways?), I think this is the storyline that was hurt the most by being part of a larger “Break-Up” theme episode. Instead of Kurt and Blaine making their own painful choices, their decision was swept up in a cynical haze of “Everybody else is breaking up, so why shouldn’t we?” fever. For Kurt and Blaine’s sake, I wish “The Break Up” had been as tightly focused as Season 3’s “The First Time.” If this hour had stayed primarily in New York with Rachel, Kurt, Finn and a visiting Blaine, it might have played more genuine and less contrived.
HitFix review of 4.04, “The Break-up”