Was writing this in the tags but it grew out of hand so putting it in a reblog instead. Though brain is fuzzy so bear with me.
The Kaidan is boring and whiny thing never made sense to me. He has so much angst potential and you don't even have to do any work for it, it's right there in the text. He has a horrific backstory.
He was one of the first human biotics which made him something other, something hated and feared, likely considered inhuman even. Went through hell and back as a child in that training camp. While trying to stand up for others. Has constant chronic pain with migraine flare ups that can and have lead to others taking their own lives. Not to mention the constant knowledge his implant may very well lead to his gruesome death someday if he keeps using his biotics.
He has all the markers for a good drama character for fandom to go wild over, save on thing. He isn't dark and broody enough. He doesn't brood, sulk, or became snarky mcsnarkerson who has a devil may care attitude and will frequently make rash dangerous decisions that get himself and others in trouble. He doesn't make his pain his entire identity.
What he is, is kind. He went through hell and it only made him kinder.
He's both the most stable of the group (if a bit too self-effacing in the beginning) and the one with the most emotional maturity. Everyone else on the team is practically screaming their issues in Shepard's face (affectionately) the moment they meet. ME follows the trend of many an RPG where the MC needs to fix all the issues, and thus also the backstory character drama.
But Alenko is very low on backstory character drama. You aren't asked to find the turian who abused him, or get him a new implant or anything like that. None of his quests really revolve around fixing him, or protecting him from himself, because he doesn't need nor want that. He gets drama, but it's not derived from his backstory. In fact you need to dig for it, since he doesn't wear it on his sleeve like so many other characters. He's just quietly dealing with his own stuff. He is a complete person when you meet him, neither expecting nor asking Shepard to shape his morals or to fix his mess, fix him.
In fact his morals won't even bend for Shepard, even when he loves them. As shown by his response to the whole Cerberus thing. He's frankly the only one with a normal reaction to the whole mess, and the only one who doesn't put Shepard on a pedestal, but holds them accountable for their actions, even a full game later.
This is also where I think the accusation of him being whiny comes from. Because he's the only character who doesn't instantly go yay Shepard's back, everything is cool now. But frankly the fact no one else did, especially people like Anderson, was one of the things that to me spoke of structural problems in the story. I like the second game, but I think it has serious plot holes that led to many of the issues in the third game. But that's a topic for another day.
He is his own person, with or without Shepard. While he was hurting after losing her, he didn't entirely go off the rails like several of the other companions. He carried on. And much as I like many of the other companions (and their angst), he truly is the healthiest love interest for Shepard.
Kaidan is really only boring if you don't bother to look past how he is initially presented. If you don't care enough to get to know him better. And I think that was the whole point of his character. That everyone always looks at him and sees only what they want to see.
The humans likely saw kid him as a dangerous anomaly, an inhuman freak. The Turian at the training camp saw a weakling human that didn't know its place. Fellow soldiers saw a spineless soldier who just followed orders without questioning. Many, like some of the player base, likely saw him as a boring plain white man who thus probably had no problems or personality whatsoever. Because he was too gentle, too boy next door, too Canadian.
Meanwhile what he actually is someone with a lot of talent. Being a strong skilled biotic even with the older faulty implants. He was kind and strong enough to stand up to the Turian trying to abuse him and the other kids. He follows orders because he respects command, but would not bend his morals even for a romanced Shepard. And he's a man who carries great trauma, chronic pain, suffering of all kinds and is thrown just as much into this shit situation Shepard is going through, yet chooses not to make that anyone else's problem.
Kaidan is kind.
And if that's boring, then we could really use a whole lot more boring in our lives and fiction alike.