It's my argument that some of ME1 and large parts of ME2 & ME3 did a terrible job with the OVERALL arch of the series. Given that a sub-optimal ending was likely and what we got [IMHO] was an @sspull of epic proportions to try to wrap up a story that didn't lead well to ANY particular, satisfying ending.
To rephrase I'm a FIRM believer that the author needs to know the ending of the story. They then need to make sure that the events, plots, characters, antagonists, etc. of the story build to and support the ending you have in mind. IMHO the first 99% of ME failed to support not just the ending we were given but I don't see a way to craft a REALLY GOOD ending without re-architecting earlier elements.
When you buy any kind of product or game, there is no guarantee that you will have a good satisfying ending. Some people did find the ending to be satisfying (myself, others), but maybe not everyone. That goes with anything. Some people didn't like how [random] series ended, but another guy might have thought the ending was really good.
The job of a writer isn't to tell and explain everything. It's to tell and explain what needs to be told and explained. And this is not what people want to be told but what the story needs from the narration to develop its own structure and internal logic. That's writing.
When I first finished ME3 back in March 2012, I had enough going into the ending to know what was going on. It didn't really feel out of place for me. I wasn't confused by what was happening.
Can you explain how Steve Cortez got back on the Normandy after his shuttle crashed in time to have a holobye at the forward operating base?
Who said he was back on the Normandy at that time you talked to him? Maybe when he survived he's still on Earth? The hologram of him doesn't show you the background where he is. When talking to Jack, she said she was south of where you were. Not everyone was on the Normandy. How did Garrus go from being at the FOB to being on the Normandy in the EC? That might have happened off-screen. Not everything needs to be shown (see 3 hour movie example).
Here's another one, why does the Normandy in the EC when picking your squad up look like the one from ME2? The current Alliance Normandy doesn't have big fans in the bottom of it. Why is the guy who hands Hackett the note that "someone made it to the Citadel" the same guy who was killed in the beginning of the game? Perhaps this is a sign from Bioware to tell you something isn't quite right. This was freshly made content, after the game was released, mind you. Not stuff that was unfinished.
The lack of Narrative Cohesion in the game's last 20 minutes is appalling.
Narrative coherence, you say? I think I posted a few links earlier on page 6 with an explanation for the ending from someone who worked on the game itself (yes, someone other than Mac or Casey). Go ahead and read it if you want. I don't think the answer is something you want to hear though.