Yeah, see, I don't agree with any of that. I felt like I got the perfect amount of closure. In fact, I felt like I had almost all the closure I needed before the final mission even started. All the interracial conflicts had been resolved, by me. The characters I cared about got a send off in some fashion, including one perfect send off that wrecked me with one line. It's true, you don't see all of the characters after the big climax, but do you need to? I don't. I'm perfectly fine imagining how things went down after the credits started rolling. If they gave a Return of the King-esque wrap up to everything, it would have been fine maybe if they handled it well, but, I definitely wouldn't still be thinking about the ending days later.
Again, I feel like a lot of the big choices from the first two games paid off long before the final mission started. I have compared notes with my roommate and there are no less than three big missions that played out completely differently because of various choices we made differently and/or characters that one of us had alive but the other did not. Also, the big choice you make at the end of Mass Effect 2 directly impacts the end of Mass Effect 3. I wasn't offered the third option on my ending because of the choice I made at the end of Mass Effect 2. (Even if it was offered to me, I would not have taken it.) I'll admit, it's not perfect. It would have been nice for the unique war assets that you acquired to have a narrative effect on the final mission rather than just a percentage of a bar you're trying to fill, especially since that bar can be very easily filled if you play a couple rounds of multiplayer.
On top of all of that, all of those previous choices inform that final choice, even if they don't all directly effect it. When I was presented with the options, I was frozen. No idea what to do. Upon reflecting on how I had made previous choices and how I had played the entire series, I realized there was only one choice I could make. And even if the final scenes all play out similarly no matter what option you select, the implications of the three options are wildly different and have vastly different ramifications to them. You are saying EVERYTHING with that final choice. You are saying, "This is the manner I want to save the galaxy in and this is how we will carry on as a galactic civilization from here. This reflects who I am and who I've been." You are shaping the future of the galaxy with that choice and doing so in a very personal way. Again, you don't see these ramifications explicitly, but so what? You have a pretty good idea how things are gonna go.
So, yeah. The ending worked for me.