i think some tropes resonate with public more than others. Relatively speaking each LI has some tropes and big aspects of their personality's are clishe. Alex is just one of those that have so many relatable character tropes or simply put lot of her character hits too close.
Penny is extrovert, lowkey celebrity, "the popular girl"
Daliah is eater, competitive, "the tough girl"
Annie is shy, timid, scaredycat, "the childhood friend"
Nancy is "milf"
Nova is nerd
you get my point.
Alex is the one that have daddy issues, family problems, shows vulnerability while also showing she is strong character by trying to be independent... There is lot to unpack or desire.
Also i love how you said Penelope went from favourite to least favourite because i feel like that fits my point perfectly. When you look for something long term, girls like penelope normally end like that. Great start and quick burnout. Once you get past the rush of getting the popular girl and now have to deal with whats beneath the fame, its not that interesting