Rape is not a feminist novel, because rape itself is not a feminist issue. It's a basic human rights issue. In the case that a woman is violently raped (as the novel depicts), many women experience an aftermath just like Teena's, filled with critics and skeptics, subjected to re-traumatization in court, and rejected by others. The rape is the inciting incident in Teena's martyrdom, and martyrdom means that Teena will bear witness to some kind of evil that is not easily noticed otherwise: The subtle misogyny of society.
The novel does contain gruesome depictions of sexual violence, but not at the sake of nuance. Oates's genius is evident in the character of Dromoor, whose own trauma makes him a likely companion to Teena, but even he can't quite stop perceiving her as an object or tool. Dromoor frequently makes himself out to be Teena's hero, as if it's just a matter of time before Teena gives him some sort of sexual attention. It's subtle, but Teena's acute trauma makes even the smallest infraction painful. Dromoor is an avatar of the same misogyny, except he is under the false impression that he is secretly Teena's savior. That's a pretty uncanny depiction of how many men react to sexual violence against women.
When the rest of Teena's community gets their own chance to provide some hope to the victim and her daughter, they fail. Apparently, the truth of violence sexual assault is so disturbing that people will reject that knowledge and prefer a simpler solution—even if it betrays the victim. Teena hears whispers and rumors suggesting that maybe she was raped because she was dressed like a slut. Perhaps she was asking for it. Perhaps she teased the men and then changed her mind about it.
Except that, actually, no. Teena was a random victim of a horrifying act of violence, and her beloved daughter was forced to watch. There is simply no way of treating Teena with respect and dignity while still entertaining the idea that maybe she's making it all up for attention, but that's exactly how she gets treated. The novel pretty much speaks for itself in that regard. The plot is a compendium of all the tiny different ways that people betray Teena when she needs them most.