"Whining about it won't do you any good. It's Bioware's project, their game, their franchise. "
I have to disagree heavily with you. If a person purchases a product, service, or any entertainment medium, the person has every right to complain. Even if they're just whining. Persons who pay another for service can very well rebut against a perceived error in the product, even when that product is aimed for entertainment. There are no further loyalties owed after the item is exchanged, and while you did not state that there should be some gratitude, I view what you're saying as equal to that style of argument.
"They made this for you! Be grateful!" is one way people tend to try and silence disapproving statements in regards to something the person likes. It's absolutely asinine to go that route, which I am pretty sure you aren't thinking like this so I shall not explain why it's so silly. If I'm wrong, feel free to correct me.
"It's their stuff, just leave them alone" is a slight extrapolation of what you said, but this is equally silly. If they had made this game and left it laying around for free, with no means by which you could identify and give the group some sort of payment, then I could understand this. However, the people paid for this game, they handed over their money in hopes of great entertainment, they are filling the wallets of those who worked on this game. At this point, the producers of this game are invested in by the consumers. While it isn't a solid 'stock' type of investment, it's a liquidation investment wherein the producers of this game are floating on the collective investment from consumers.
The consumers have a right to voice what they like, or don't like, about this game. There is no required action, but should people find something so aggravating that they're compelled into action, even if venting to friends who might otherwise buy this product themselves, then they should be encouraged to do so. Yes, sometimes this means just letting people bitch and whine.
"but if you were a hardcore Mass Effect fan"
No true Scotsman fallacy. You don't get to dictate what a 'hardcore' fan would think of any product. You can disagree, state your own opinions, but putting it like that makes you seem rather like a jerk. If the 'whining' of the other people who have played the game bothers you, try to speak with them and convince them they're wrong, or just state you do not agree with them and move along.
This seems like a bit of an unfair balance from a casual read, "They get to whine and moan, but you have to either be logical or move on" type of vibe. That really is what I'm going for, but this is because what they're experiencing is a more angry form of feeling cheated, above that it's a larger investment you have to make for that side of the situation. When it comes to listening to people shrieking in hatred, the frustration you get shouldn't be so primal and derp-inducing, so it's a matter of having a higher likelihood of better senses about you.
Maybe I'm being overboard in this, you may just be venting your frustration and have already carried on with your life. If not, I hope this helps to reshape your thoughts on the matter, but if you think I'm wrong you can very well ignore me or attempt to sway me to seeing what's correct about your perspective. You can do anything you like with this really. Not like I can actually limit you to those two options.
I'm personally not so aggrieved at this turn of events, due to a lack of functioning methods to play the series (360 RRoD'd and I'm poor) I can't relate to the later games right now. I very well might be right in the same boat as them, finding this to be a shitty ending that smears crap all over my love for the franchise. I may also play through eventually and find the currently existing endings to be a great work of art. I don't know, and I won't know for quite some time.
Hopefully you did not mind this large comment, just in that state where I can ramble endlessly and should honestly go lay down. Been up for 25 hours at this point.