The intended effect was that the galaxy was destroyed, according to most of the people that played it. It was clearly stated that (much like the ME2 Arrival DLC) the relays would be destroyed no matter what Shepard picked. Not only that, but we clearly see the relays breaking apart in all endings - people like to fanwank that the relays didn't completely blow-up on-screen in the Control ending, but that's just semantics.triggrhappy94 said:Going by the original ending, everyone wouldn't die.
Thus, even if the relays were just irreparably damaged and didn't kill everyone, the people left behind either had to travel for years just to get home (Krogans/Asari/Quarians), with the disadvantage of several logistics/supply problems, and for the Normandy crew stranded on the planet, there was the question of whether they had enough food to survive. No matter how many times BW tried to "Twitter-canon" their way out of it, the ending (much like the rest of the game) was a complete narrative failure. It made the series a shaggy dog story.
The EC clearly retconned their condition so that they were clearly seen and mentioned to be merely damaged instead of destroyed (along with a host of other things).