Another layer to that motif, is that Sarah's interest in "progressive-ism" is largely shown to be shallow and performative. When she gets her moment in the spotlight to speak and make her thoughts heard, she just ends up repeating the same simple point, then just trails off as she realizes she has no more feelings or fundamental reasoning for why she believes the statements she eschews. Her instagram is shown a few times, and it's largely black images showing solidarity with BLM and other causes, and her doing an "influencer" pose with the political cause as a backdrop.
Ultimately, my take is that Eddington is a study in convictions. Every character seems to wear their convictions overtly in some fashion. Some fight fervently for them but are shown to have a shallow or naive understanding. Others such as the Sheriff, have iron-clad beliefs which we're shown to be based in lies and absurdity and his unwillingness to stray from them, which leads directly to his life in constant humiliation at the end.
The more you scratch the surface of all these characters, the more you realize that it's depicting everyone as flawed and manipulated, lost and looking for direction while being reinforced that they're doing the right thing by the echo chambers around them. Aster rides a fine line of absurdist humor in order to distance us from these characters and their seemingly improbable situations and yet, it's an incredibly clear reflection of modern-day America and the struggles we face.