I really don't want to go into this again, I'm over it. Honestly, I love this series and I love that Bioware set a precedent by listening to their fans and addressing their thoughts about the endings. I don't think any other company would release extended ending dlc, for free, to at least, come to a compromise. They'd say, "Don't like the endings? Pfft. Tough. Don't play it again. Sell the game." But, I will put down what I didn't like about the endings (the originals and the EC) and it has nothing to do with Shepard living or dying.
1. Big writing mistake here. Forcing closure with the characters *before* the end of the game. What I mean here is, the FOB where all of your squadmates are standing for "one last goodbye" and you get to call your old squadmates from ME2. The mistake is that the ending is at least an hour away and these characters' story is not finished being told. We don't find out what happens to them when the game "ends." There is no closure.
Fixed with the extended cut. Mostly.
2. War assets don't show up at the end. No clips of past squadmates, no geth, no quarians, no rachni, just a bunch of data entries and a number.
3. It's Shep and two squaddies running through the dark, a few voices on the radio, a couple of makos and 1 clip of a reaper destroyer uh destroying some krogans, turians and an asari commando. Horde mode near the Citadel Beam, push the button. I expected something like Mass Effect 2's Collector Base, where your decisions do matter and people could die if you screw up. You know, 3 of your squadmates go this way, 3 go that way, 2 head back to the Normandy. Maybe even a boss fight with Harbinger. But, no. That would have been too "video gamey." I'm playing a video game, I expect that it just might be "video gamey."
The EC at least shows how your squadmates got off the battlefield even though it makes absolutely no sense why Harbinger didn't just blow Normandy right out of the sky right there. Handwavey explanation; the reaper iff makes the Normandy look like a reaper and reapers don't have "eyes," just scanners.
4. The long slow shuffle. You know what I mean.
5. The magic elevator. Oh, sorry. Mass Effect fields. Nevermind.
6. Shepard does not act like Shepard should during the conversation with the Catalyst. He/she should immediately be distrustful from the word "Wake..." because the Catalyst looks like the kid.
7. The choices. There should be one more choice here. My Shepard would say, "Why can't I shut both you and the Reapers down? Right here, right now. Where is that console? I've decided not to use the Crucible. No shooting of pipes, no grabbing of controls that disintegrate me, and definitely no jumping into an energy beam. I will rip everything in here apart with my bare hands until I find your hardware."
8. I still find it hard to believe that Joker (and everybody else) would leave Shepard stranded. I'm just not buying it, man. See also the end of Mass Effect 2.

If Shep dies afterwards, cool. Worthy sacrifice.
I could go on but I won't. This is long enough and it's already been talked to death by me and everyone else here who disliked the endings. Personally, it had nothing to do with Shep dying.