To me, this ending creates a much more interesting ground for new games in the series (what with the name giving relays are gone) than as when we'd just had a "Reapers are gone, that's it lol" ending..
[spoiler:496a158288]
Except if you ask me, even a ''reapers dead lol'' ending would have fit the series more. This kind of depressing, no-matter-what-you-do-you're-screwed ending may fit in, I don't know, Cyberpunk (note how the three endings are basically lifted from Deux Ex 1), or sad stories like Red Dead Redemption, but Mass Effect is a space opera that always at least proclaimed choice matters and victory s possible in the end. It also had well established thematic elements, such as free will (Geth subplot, Jacob's loyalty mission), the right of a species to exist (again the geth, the Genophage), or the fact that Shepard fights and can win no matter the odds (the whole damn series). All that is thrown out of the window, some Deux Ex Machina god-child throws some determinist bullshit at you, you can't even argue its lack of evidence or its conclusions, then you choose between green explosion, red explosion or blue explosions. How the hell does this fit the game?
Also, yes Eezo is a fictionnal element, but the use the universe makes of it is well-documented and makes sense in context, which is what science-fiction is all about. The endings magically destroy all synthetic life (shouldn't Shepard die then, since he is half-synthetic? What about VIs? What are the ''critera'' for being considered synthetic life? Not explained at all), control the Reapers (OK this one is less space magic, just send the right signal and off ye go; but if you can control them, why not just shut them down?) or turn every being in the galaxy (or just sapient species...?) into a half-robot, with a ''new DNA'', instantly, which is space magic of the highest order. No foreshadowing. No explanations. It just happens, accept it bitches.
Also, about the lack of closure, I tought this one was obvious. You spent three games uniting the galaxy, fixing problems left and right... But it doesn't change anything. Let's take one example; the Quarians. You can exterminate them on Rannoch. If you don't, the Migrant Fleet comes to aid the fight against the Reapers. Except, with the Relays destroyed, they can't return to the homaland they just liberated. Worse, they are stranded on Earth, an amino-based planet, while they are dextro-based life forms. They are doomed to die of starvation eventually. All of them. So are the Turians present. So who the hell cares if you save them or not, in the end, since they are all going to die anyhow? That's just one example. What happened to the crew? Am I supposed to believe 20 people tops can found a prospering colony on an unknown planet? And again, Tali and Garrus are doomed to die of starvation, unless the planet is dextro-based, in which case the rest of the crew does, leaving EDI Forever Alone... unless she magically got destroyed in the ending. What a bright future for the people who have followed us three games long! At this point, better to kill them off in the Suicide Mission. At least they die in a blaze of glry, rather than fucking starving after being stranded for no goddamn reason. It's completely against the character of everybody on board the Normandy to
escape the battle and leave Shepard alone. They never did this. No one on board would ever approve. Not only that, but you squadmates were all on Earth by the time of the assault on the Beam. Yet, in the time Shepard destroys the relays, they got back on the Normandy, abandonning him (wtf) and had time to enter a Mass Relay corridor, travel in those is near instantaneous, btw, hell of a coincidence they got cut at that time. It's not ambiguous, it doesn't make any kind of fucking sense. The fleet of the galaxy are stranded on Earth, which is devastated and doesn't have the ressources to sustain them. This is simply fact, there's no ambiguity.[/spoiler:496a158288]
Again, I kinda see your point, if you like it so be it. But there are very real reasons why one could hate the ending.
EDIT: to further support my point, I give you this piece of Gamespot garbage
http://www.gamespot.com/features/why-bioware-shouldnt-change-mass-effect-3s-ending-6366066/
Compare with this in-depth article (spoiler warning) :
http://www.gamefront.com/mass-effect-3-ending-hatred-5-reasons-the-fans-are-right/1/
I don't give a flying fuck about ''creator freedom'' when Bioware has promised different and fulfilling endings and has broken these promises like no tomorrow. Not the first time, yes, but its their biggest offender yet. I coped with a lot of things from them, but I just drew the line. ME3 was very enjoyable, but no response to this means I will buy future Bioware games in the bargain bin at best.