Simple- she's got no death points between three games right up until the end where you have to mess up to lose your teammates on the beam run. Characters introduced in Mass Effect 3 don't count as they haven't gone three games without dying. Joker gets less one on one material than Liara in the games she stars in.
Liara can't get shaped to your Shepard and while my primary Shepard considers her squad her family- it doesn't hold true to my Renegade, picky and semi psychotic Shepard and the stalker bit is creepy. It's not flattering to listen to her character try and insert herself with so little grace that I cringe like I'm reading bad fanfiction. It makes absolutely no sense for a character who insists she is Shepard's best friend not make comments in the second game, responding to your Shepard and how Joker got involved, etcetera. Her self-centred ego trips turn situations into 'look at me, I'm just awesome' so yes, I only take her when it's necessary or the plot demands it, like on Noveria.
It's bad enough that despite my struggle to choose between teammates for most missions, I never regret discarding T'Soni. My advice is next time the writers need to treat all the main squadmates equally, extra material dependent on personal interaction although I don't hate her. Her character simply frustrates me in a railroaded and often blandly favoured child of the writers.