I'm really glad that you enjoyed the game OP.
Personally, I didn't - and not just for the reasons that you cited in your reservations, although they are certainly in the mix too.
Right from the beginning there was something wrong with ME3 for me. It seemed to be actively trying to push me out of the player experience. The Shepard I was playing seemed totally alien to the one I had been role-playing for the two previous titles (and I'm not just talking about the facial import bug).
She wasn't acting the way I wanted through the clunky auto-dialogue (did you know she was angry about James crashing the shuttle? I didn't know she was angry about the shuttle - and I'm her); she wasn't responding to events in character, or the character I knew her to be (all that emotional manipulation with the stupid dreams and the dialogue about regrets that my Shepard never had...)
The story became chokingly linear, stripping away all exploration and side missions in favour of a strictly regimented progression that allowed for only minor variation. The fetch questing was a meaningless, confusing chore (and I say that as someone who adored both the Mako and Planet mining). And none of the decisions I was making past or present seemed to be having any impact on the universe at all:
'How are you enjoying being the Council Leader Anderson? ...Oh, you're not now? Oh, well. At least we don't have to worry about those Racchni... wait, they're everywhere?! Okay, okay, just so long as the Collector Base is destroyed and the Human Reaper is gone then I can.... what?! For the love of...'
And all of this just added up to an EMS score - that did nothing in game except expand three options I could not have despised more. After the rich potentiality of the multiple endings in the Suicide Mission of ME2 I cannot describe how underwhelming EMS turned out to be...
And then, yes: the ending. Literally one of the worst, most ham-fisted attempts to be 'deep' that failed on every level: logic, emotion, theme, character consistency - everything was eviscerated in a nihilistic blaze of hate.
And if nothing else, it just threw into stark relief how horridly mishandled the rest of the narrative was: I realised that the whole time, while we were meant to be experiencing these immense feelings of loss, sacrifice, and the brutality of battle, we were building a giant magic 'I win' button (that was invented from 'dreeeeeamz'). We were meant to feel the sorrow and tragedy of warfare - while building a floating god mode button.
And I couldn't even say that it was all just meant to be vague and poetic, because they stabbed all of the metaphors of hope and inclusivity to death when they force you to use the reaper's tactics to survive in the end.
No, for me the whole thing was an enormous disappointment, and shared little in common with its predecessors. It was a pretty game (when the faces weren't glitching out like zombies and people weren't jittering against walls), and the action was tight (but that was not what drew me to Mass Effect in the first place). There were flashes of the original beauty of the games in some of the character moments, but to me it played more as a linear shooter like Gears of War, and that was not what I wanted at all. All of the role-playing elements I had come to cherish were stripped out, and what they were replaced by seemed wholly unfamiliar.
But truly: my rant notwithstanding , I am glad that you enjoyed the game. It wasn't at all what I wanted, but I am glad that it worked for others.