You know why season 5 slexie is such a great ship? Because Mark and Lexie see each others worth while everyone else overlooks them and takes them for granted.
Literally, the first time they ever talk on-screen, Mark sees how George ignores Lexie and how she willingly puts up with it because she’s desperate for attention, and says, basically “I don’t know you, but have considered having standards for how you should be treated? Because you deserve better than this.” Everyone else sees Lexie as this peppy little puppy who’s trying too hard to be loved to actually be loved — the girl was so desperate for Meredith’s approval that she eagerly ate something she was allergic to just because Meredith made it!— but Mark instantly sees her as she is: a genius. Loyal. Driven. Talented. Resilient.
They could have gone for the low hanging fruit and had the resident manwhore seduce her because she’s so desperate for affection that she’d fall for anyone who gave her the barest crumbs (hi George!) and then have him be surprised when he actually falls for her, but they don’t . Instead, Mark likes Lexie because he sees her worth and tries to give her the feast of love he thinks she deserves and that no one else tries to offer her. That “you take her home or I will” line? That’s Mark saying “I don’t think I’m good enough for her, but if no one else will step for her, because not good enough is better than the nothing she currently has”. Mark adores Lexie, he’s all in, his end of season conflict is him realizing that Lexie might not be as serious about him as he is about her, because he understands the value of what he’s got and doesn’t want to let Lexie go.
(Side note: I would LOVE a season 5 AU where Mark is the one to take Lexie home)
Lexie, meanwhile, is one of the few people who doesn’t treat Mark as lesser because of his past. The harsh truth is that if you want people to change, you have to let them. When they improve, adjust your treatment accordingly. Because if someone is always going to be treated like the worst version of themselves, they don’t have much incentive to become a better version. But everyone likes to hold Marks past and reputation against him, even when it has no bearing. Mark never acts inappropriately with Lexie. Their first conversations are all Mark encouraging Lexie to stand up for herself, or being impressed by her skills. Yet because he treats her well and offers positive feedback, everyone immediately jumps to the worst conclusions.
Even worse, people, even Derek, Mark’s supposed best friend, assume that in this relationship, Mark would be a bad partner to Lexie, presumably acting selfishly and callously. This is despite the fact that Mark and Lexies relationship caught their attention because Mark is warmer, more caring, and more encouraging with Lexie than with anyone else, including his laundry list of hookups, and that Derek and Meredith are still ignoring her at this point. He was a whore, he can’t possibly be a decent partner to anyone ever.
But Lexie never brings that up. Not even as an insecurity, ie “you’ve been with so many women, what do you see in me?” To her, his past is just that: in the past. What matters to her is how he treats her in the present. She doesn’t like being in a secret relationship because he makes her happy and she doesn’t want to hide that. When others make lewd jokes, Lexie knows damn well the problem is outsiders and not their relationship. When Mark and Derek are fighting, it stresses Lexie, but she never wavers in her devotion to Mark, because she knows Derek has no place to warn Mark away from her like she was a child. Lexie sees Mark as someone skilled, who cherishes her, who takes steps that scare him because they matter to her, who pushes her to demand more from the people around her and then shows her what she should expect.
So while everyone else sees Mark and Lexie as a whore and a immature puppy, they see each other as an encouraging partner and an overlooked genius, and that’s what makes their relationship so fucking good.
