I agree that the ending was about choice - not about all your previous choices, but adding one last big choice, that would implicate an unknown future. It was like that time when I had to choose between killing and releasing the Rachni queen.
My first playthrough tells another tale though. Early on, I decided that I was going to stop doing sidequests, and just focus on the main missions. I read Thane’s email, but I never saw him in the game. Didn’t meet Jacob or Samara, and only encountered Miranda in time to see her get killed by her own father.
An email arrived, from Wrex, announcing Eve’s death in the bomb blast I hadn’t prevented.
On Earth, after Cortez perished in his shuttle, only Jack was there for a chat with the intergalactic phone booth.
And my meeting with space boy ended with the choice between refusal (and forfeiting the war), and burning Earth to a crisp, with Destroy. So Earth burned. The Normandy crash landed, and its door never opened. This playthrough breathed an overwhelming sense of loss.
On my second run, I did everything, reconnected with everyone, got three choices at the end, and chose Destroy again - because I didn’t want Shepard to turn into a god with an army of vengeful angels, and because the promise of eternal peace among the green glowing masses sounded to me like the destruction of individuality for everyone in the galaxy. Sorry EDI, sorry Geth, but sacrifices had to be made. Nothing personal.
My biggest issue with the game was the neutering of the Rachni. After that encounter in ME2, I’d expected this game to be very easy: Shepard makes The Call -> Rachni start singing, descend on Reapers, tear them apart -> Game over, you win!
Granted, from a gameplay perspective, that would be a bit thin on content.