There's a difference between a character that's a star and one that's the heart and soul of a show.
On One Life to Live, Vicki Lord was the core of the show. Her relationship with her father colored her life, but unlike Erica Kane on All My Children, she suffered from too much of his smothering attention. Vicki was a character who may have made mistakes, but she was a good, caring person who always felt the burden of her responsibilities and was the dependable matriarch from a very early age. The viewers always understood the psychic toll that responsibility took, and it was dramatically underscored by the appearance of her Dissociative Identity Disorder alter-ego, Nikki. It was a device that was sometimes used cheaply when the writers wanted to get out of a corner with the character, but most of the time her long-time portrayer Erika Slezak was able to play it with the sensitivity it deserved. And while Vicki was beloved by almost everyone, part of her enduring appeal was the long-term rivalry she had with her stepmother/frenemy Dorian Cramer Lord (among other last names).
Vicki was central to the story, but One Life To Live pushed the envelope with other storylines as much as it could. Head writer Agnes Nixon famously took a lot of criticism for her early attempts to introduce socially relevant stories, whether it was a black character who "passed" for white, a gay teenager in the Nineties or a story about HIV, among many others. It also moved to include characters of different ethnicities and integrate them into the main storylines without tokenism while other shows were hoping to put that off for as long as possible.
The secret to One Life To Live's success, however, wasn't cutting edge storytelling but rather it's focus on strong families. The Lords, Buchanans, Cramers, Vegas and others may not have been the happiest, but when push came to shove, they had each others' backs. The writers also, for the most part, understood the importance of growing family trees and mixing them up on a regular basis.
The lesson: complicated characters and their stories work best when they're told against a backdrop of strong core families.