No one is defending starkid, the whole point is that a happy ending would be out of place with the intended Phyrrhic victory tone.
I'll preface what I am about to say with that this is my opinionated opinion and that I am fond of the Mass Effect series;
I am of the opinion that a story ending in a Pyrrhic Victory has to have earned that ending in order for it to fit the story and I’ll clarify that when I say earn, I mean that it has to build up to that ending and I am of the opinion that Mass Effect did not properly built up to the endings that it had. Having the characters states that this will end tragically is not enough: the story has to portray this as a plausible ending in terms of tone and narrative.
The ending of the first season in Telltale’s Walking Dead series was a very tragic and bittersweet one but it was one that the season had earned itself and therefore it fitted as the ending to the story. Throughout the season, each episode managed to keep the atmosphere of the apocalyptic setting and illusion of choice aside, manage to drive players to make decisions and justify them as a person in such a setting would.
An example of this occurs in the second episode wherein the player character is given the task of handing out food for the day. One half of thing is that all the food that remains for the day is half an apple, a piece of beef jerky and two pieces of cheese and crackers. The other half is that the group is composed of about eight people - nine if you count the recent arrival. Two members of the group are children below the age of ten. Everybody is hungry and it has become so bad that some are starting to suffer deteriorating effects from hunger. Something interesting to note is that the player can choose to have the player character keeps a piece of the food for themselves or not. Another interesting bit is how people react depending on who you give the food to: if you feed the children, the parent of one of the children will be satisfied with whoever else you feed and will refuse to take any food you offer them if their child has not eaten yet. If you attempt to offer the food to a person you saved in the prior episode, you’ll have to insist that they take the food since they want to see you and the child connected to you fed. Some will react negatively to not receiving any food while others will not even if they really wanted to.
An example of this also occurs in the second episode wherein the player character and their group stumble upon a car with light on in the woods. After approaching it carefully, they find keys in the ignition and that the car has supplies in and not just food but medicine, clothing and so forth. The question remains, however, is who left the car and if they are still alive. Members of the group decide to take the supplies and reasons that it is abandoned. The player is left to decide whether or not they agree with this decision and will participate in taking the supplies.
An example of this occur in the third episode wherein the player character is on a food run with another member of their group and from a distance, they witness a girl be cornered by walkers and subsequently bitten by them though not yet taken down by them. The non-player character hitches on the plan to use her as a distraction for the walkers so that she’ll lure out the ones that are difficult to see. He reasons that she is already dead and as a distraction, she’ll buy them more time to scavenge food that they desperately need. The player is left with the choice to either mercy-kill her or leaves her alive to slowly be devoured alive by the walkers. If the player chooses the former, they’ll be left with less time to gather the supplies but if they choose the latter, they’ll be left with more time but has to listen to her dying screams until the walkers finally end her suffering. The interesting bit about this is also that you gather the supplies manually by clicking on them and that it is possibly to gather a large amount of supplies while deciding to do the former. It is, however, more difficult for some due to the decreased amount of time they have to do so.
Basically, a lot of choices focus on decisions that are morally questionable but may be necessary for the group’s survival. The season tries to avoid inducing a sense of apathy in the players by having moments that can be hopeful and heartwarming. The story earns it’s bittersweet but satisfying ending by having a very bittersweet tone: you and your group is constantly dogged by reminders of the state of the world such as through food shortage and though you may survive for another day, these reminders take their toll and you and your group suffer it’s effects in more ways than simply through the losses of your fellow members.
Besides being a stellar game, I bring in examples from Telltale’s the Walking Dead series because it did know how to build up to the bittersweet ending it had. The player had choices including some that mattered but nonetheless remained aware that they would not be able to influence or prevent everything that occurred. They’d suffer losses, they’d suffer setbacks and they’d be utterly helpless in some moments because all of those things were in the nature of the story. They’d also be able to believe in an ending where the story concluded in a way that was not downright bleak because they’d lived through the losses and they’d gotten back up after the setbacks the best they could.
Then there is that the developers banked on the players caring about one person making it through the story alive and well: Clementine. They’d banked on the players building a rapport with Clementine and with it, a wish to keep her safe which some of the child-hating players even shared: “If the only person who makes it through all of this is Clementine then I’ve won.” "As long as Clementine makes it through all of this, I'm happy"
It worked: Clementine survived the season and the execution of the last scene she had with the player character created a very depressing but still satisfying conclusion to the ending. Despite what happened to the player character and the ambiguous note at the end, a lot of players still felt a mission accomplished. It was hope answered with hope.
I am of the opinion that the Mass Effect trilogy did not properly set the stage for the story to conclude itself in the ending it did.
An example is if we only look at Shepard’s “sacrifice” in the endings. A lot, if not most, of the losses that the player and the player character can suffer throughout the trilogy is dependant upon the player’s choices meaning that if the player wills it, the story can have a very small amount of losses that the player is invested in. This basically means that the developers can allow players to shape the story in such a way that the ending the developers have created becomes disjointed.
An example of this is the Suicide Mission in Mass Effect 2: the player can make a mission that was portrayed as and named a suicide mission into a casualty-free mission. This adds weight to the players’ idea that the player character can overcome even the biggest odds as long as the player makes the right choices for it: they based the entire game of Mass Effect 2 on this idea.
This idea proceeded to be carried over in Mass Effect 3 wherein the deaths of most of the people the player can have a personal investment in are dependent upon the player’s choices. Allow me to list some examples; Tali’Zorah, Ashley or Kaidan, Mordin, Wrex, Samara, Kasumi, Miranda, Cortez and Grunt. Even minor characters can survive such as Conrad Verner depending on the player’s decisions.
TL:DR - My point basically boils down to this: the developers of the Mass Effect series did not build up a story that strongly enough supported the endings that they made and so the endings became disjointed to the rest of the story. By executing the story the way they did, they unintentionally allowed the players to shape the story in such a way that their intended ending would no longer be able to fit because the variables could and did create the build-up for an entirely different ending.