Well, taking those assumptions, 1. it's clear that AOC has a prominence as a progressive and popular political figure - therefore her positions are often a starting point of awareness & understanding for those they are presumably trying to reach or critique.
2. Even if one doesn't believe in the value or workable participation in the democratic processes, it's undeniable that the actors involved have either access, audience, represents or has direct responsibility for the actions of the state/govt & its policies, so 'caring'/critique have purpose.
(trying not to speak on behalf of others. I'm sure the varied left in question would have their own, more refined and particular answers.)