The intersections and overlap between the classism and misogyny portrayed in YR on one hand and racism on the other are a really valuable point of discussion, and we could (and likely should!) definitely talk about them more.
However. No offence to OP, but I feel like we should first refresh our memory of the examples listed:
August did not feel entitled to Felice's body but her hand in marriage (as he tells Erik). This is because she's a popular highborn girl from one of Sweden's richest families, and he's a popular highborn boy from a family deep in debt. She is the one who initiates the sexual side of their relationship, and if we look at their highly uncomfortable sex scene, he doesn't look particularly into it either. He's misogynist and a terrible lover to her, for sure, but the relationship is not based on him using her for her body.
August did not scapegoat Alexander. That was Wille. If Wille hadn't done it, August wouldn't have been able to persuade Alexander to agree to "take the blame" in S2. August did treat Alexander as an errand boy and make him carry the Society's drugs, though.
August did not assume Simon had drugs and couldn't say no. He assumed Simon had easier access to alcohol on account of living outside the school. He first tried to buy drugs off Sara, because he knew she had them, and when Simon forbade it, offered to buy them through him instead. There was no coercion in either case, he simply refused to pay afterwards.
August was not affectionate with Sara from the start. He called her a freak and used her to pre-emptively get even with Felice in case she cheated on him with Wille. He only became affectionate with her after she pursued him when he was at his lowest in S2.
I think one pivotal question we should be asking is whether the writers did any kind of sensitivity read or considered how adapting some of their characters to the ethnicities of their diverse cast would also make racism relevant to their storylines. One example is Simon's drug dealing plot, which was likely meant to just be about classism when the character's ethnicity was unspecified (we know Malte also auditioned for Simon). But when they cast Omar and made Simon POC, they don't seem to have realised that viewers might also connect the drug plot to harmful racial stereotypes. Or Alexander's treatment - in S3, it's revealed that Erik treated August much the same way, but in casting Xiao-Long Zhao as Alex, they had already added the element of a white kid oppressing an Asian kid.
And yes, because August starts the show as the epitome of all these privileges, those additions do also impact his characterisation. They even seemed to understand that when they wrote him that line about rowing as a great equaliser, but they never called back to that. Unless we count Vincent being blatantly racist towards Marwan in S3 and August weakly trying to call him out, but that almost implies that racism was one of the things Vincent took away from August with the prefect position and rowing captaincy, so...
If we look at the broader story of the show, I do think it's largely explained by lack of consideration/awareness by the white writing team. Their characters were originally written as white, and sometimes they failed to adapt them fully into POC. That's visible in some aspects of Felice's storyline, most notably the one-sided portrayal of her and Wille's friendship and her lack of interiority or a storyline of her own in S2 (Black Best Friend trope vibes). I do really like her own storyline in S3, but I wish they'd been more consistent in writing her as a POC throughout the show, and the other POC characters were sometimes treated with even less care. Just look at Alexander having no lines whatsoever in S3...