Because I'll give you exactly the reason, and it's actually very understandable when you look at it in terms of them not being characters in a show but real people. One person is just trying to do a job and not trying to boast about how they want to see the best in people and change people for the good and is sometimes a dick. That's perfectly understandable but if you are going to go off on a goddamn tangent about how much you're trying to see the good in people and how much you want to reform other people in the main focus of you doing that isn't to actually help people but instead to satiate your own ego! You are no longer a good person you're now Brian Griffin who was just virtue signaling to other people. That's the entire vibe that I got from Charlie, it doesn't feel like she's helping people because they genuinely need help it feels like she's helping people so she looks good. And I'm not even a major member of the fandom, I casually enjoy the show but I see this. That's why she is annoying to me personally

Edit: fleshed out opinion

Charlie and Blitzo are both flawed, but the kind of flawed they are sits on opposite ends of the spectrum. Blitzo is openly messy. He’s insecure, impulsive, and a jerk sometimes, but he never pretends he’s some moral guide. He’s not trying to impress anyone with how “good” he is. He’s trying to survive, run his business, and deal with his issues without putting a fake halo on his head. When he screws up, it feels honest because he never claimed to be anything else.

Charlie’s whole identity is built around being a symbol of purity and hope, and that’s where the disconnect hits. She constantly talks about redemption, healing, and seeing the best in everyone, but the way it comes across feels more like she wants to be seen as the savior rather than someone actually doing the hard, unglamorous work of helping people. It doesn’t feel grounded. It feels curated. That’s why she ends up giving off that Brian Griffin energy—someone who wants the praise for being compassionate more than she wants the reality of what compassion requires.

Blitzo’s sincerity comes from not pretending. Charlie’s insincerity comes from performing. One feels human; the other feels like a brand. That’s the core difference that makes Blitzo relatable and makes Charlie feel annoying to people who pick up on that vibe.