I disagree.
The most central theme of the entire trilogy was the internal struggle between Shepard's paragon and renegade sides. This was the entire point of the trilogy, right from the get-go. It's a central mechanic to the game, it's a central part of the narrative, and it's a central part of what draws the player in. The whole space opera thing is just a platform to explore the philosophical and moral dilemmas it brings up.
The ending fits this perfectly. Yes, it gets abstract, and for a game whose most compelling aspect is not what takes place on screen, but what happens in the player's mind, abstract is fine.