I've heard all kinds of bull**** analogies to justify the idea that Bioware should stick it out. From general "artistic integrity" comments to actually having it compared to a great painter changing a famous painting because the "fans" liked green sunflowers better.
The analogies are bull****. Mass Effect 3 isn't art, it features some art - there's a fundamental difference. Pure art doesn't have to conform to mass user standards. It can be whatever it's author wants it to be. Mass Effect is a mass consumer product, a piece of pulp, an entertaining space game where you make a lot of galaxy-affecting choices in an effort to save it. It's a piece of escapism, a fictional universe-based epic story to get lost in after a hard day's work. It is not a piece of classic literature meant to have us ponder about the reality of man's existence. It's a game where you command a space ship, seduce blue alien babes and shoot at zombie like things, feeling unique and like a galaxy saving hero - something most of us can really only experience through interactive fiction like this.
So, once you spent 5 years (or so) telling the fans to keep their saves, presenting them with options and decisions that you keep promising will have a meaningful impact on the endings, and then fail to deliver that, it's basically false advertising. When you spend that same time making them care about the characters, and then fail to provide any sort of closure regarding them, it's not false advertising, but it is bad storytelling. As is a plot hole ridden end that really makes no sense.
So why shouldn't we get a DLC that at least expands on the endings, fixes the plot holes, and puts things in context? I agree with the general concensus that the worst problems of the endings are the fact that they throw your choices out the window, and contain massive plot holes. People say they're fine with sad endings as long as these issues are addressed. I'm fine with them too, but in a game that's all about player choices, why force only sad endings? What is so wrong about coming home from work, immersing into a fantastic sci fi universe, winning over the blue alien babe and saving the galaxy while we're at it? I know dark and gloomy is fashionable these days, but damn it I just want a happy hero ending, and no - I don't think it's a bad thing.
But "artistic choices" and "artistic integrity" aside, there's a simple reason why this should be fixed. Before ME3 even came out, I always had a plan to first import my ME2 savegame, complete it, and then replay all 3 games in sequence. I don't want to now. The last few minutes of the game completely killed the replay value of the franchise - at least for me. For 3 games that can play quite differently each time you play them, that's a shame.