Giving the players choices during the finale is also sometimes overrated.
I don't think it was really necessary to give Shepard a choice in how to resolve the Reaper threat. DA:O's ending for example was largely praised, and it didn't provide any means to resolve the Blight other than to kill the archdemon. I think ME3 would have been far better off, if like DA:O, they kept it simple. It didn't need a twist in the end game, or new, unexpected solutions to the Reapers.
I agree... the game choices determining who Shepard was and what he believed in at his soul had already been made by the player.
I view the endings as an already dead man reviewing his life just as some interpretations of "Ulysses" put forth (and Dante puts Ulysses in hell). To me, anything past the point of Shep crawling towards the console is a review and an imagining perhaps of what he would have like to have seen done if he had lived a moment longer. He dies then and there never having been given the chance or the power to actually resolve the Reaper threat (akin to "Death closes all" - we humans simply cannot avoid dying).
i think that, given that BW did decide to add this reflective element, they should have perhaps included a "final breath/sigh of satisfaction" in all the possible endings of the game, rather than dissolving Shep's corpse in 2 of them. The dilemma/choice for the player in the end only being to decide whether or not they were pleased with the choices they had made throughout the game... and Shep simply never knows how the Reapers were defeated or allied with or controlled or even whether or not they were defeated... and we all move onto a new story in a new galaxy.
Of course, to go that route, they would have been seen as absolutely making it so the player's choices didn't matter... but in reality, in a reflective sense, the choices to that point should have very much mattered to Shep in the only way any of our choices matter to ourselves in death.