I’m sorry Anon, I’m not quite sure what you mean! Are you saying Eren might “sisterzone” Mikasa or that the writing is? I’ll answer both, if that’s okay.

The writing definitely is not “sisterzoning” Mikasa. Mikasa’s feelings I think are abundantly clear after chapter 50, in which it’s entirely possible she was moving to kiss him during the Clash of the Titans Arc. For the record, I didn’t ship it until chapter 50, though I did always think she had feelings for him.

I don’t think it’s a realistic reading to deny that Mikasa canonically has romantic feelings for Eren–it’s kind of blatant. Furthermore, Falco’s feelings for Gabi also clearly have a romantic component; pretending to be siblings doesn’t really change that and I just don’t think that situation is the best comparison as I doubt it’ll have further relevance.

As for how Eren sees Mikasa, that’s a different story all together, and Isayama pointing out Eren sees her as a motherly presence is not the same thing as saying Mikasa sees herself in a maternal sense (but there is some Oedipal-ness there). And it’s true–Mikasa is always trying to protect him as Carla asked her to do, but she would have done that anyways because she pretty clearly sees him as a major part of her identity, even to an unhealthy extent which I’ve talked about before, and that protectiveness is actually pushing Eren away in some sense. I do think the end goal of Mikasa’s arc has to be growing away from Eren; that being said, it’s not unrealistic to imagine that Eren would realize they could have had a happy future if, if, if.

If the circumstances of their world weren’t so cruel.

If they didn’t have to constantly fight to survive.

If Eren didn’t have a time limit on his lifespan.

If he’d decided not to go to Marlay.

Eren’s arc is tragic as hell. Even looking at the symbolism in the scene from chapter 50. Mikasa is essentially telling him she loves him, maybe wants to kiss him, and he focuses on I want to fight to save you. In doing that, he saves her, but he also loses that moment.

Eren will probably help save humanity even if Armin is the actual hero, but the cost is pretty clearly going to be his relationship with his loved ones–though I do absolutely think Mikasa and Armin will love Eren no matter how they disapprove of his actions, and I think he will love them regardless. But the closeness and the future, however short, they might have had, is probably gone.

And Mikasa knows this as she says here:

There isn’t a happy ending for them together like she’d have wanted, but she’s still clinging as we see in recent chapters wherein her clinging almost leads to her and Armin getting blown up.

To save the rest of her loved ones, Mikasa won’t be able to save Eren. I think that’s definitely where the story is going, but I do think it’s also realistic that Eren and Mikasa will have a moment wherein Eren acknowledges what could have been, and that he loves her, regardless of whether there is a romantic component.

I personally think there is likely to be (the set up is obvious, like with Touka and Kaneki in TG or Ochaco and Izuku in BNHA–it’s def a darker story with no hope for a happy ending for them, but main female character + main male character in this kind of story with a scene like chapter 50 that is clearly designed to put romance in the reader’s mind, is almost certainly intended to be romantic, plus we know Mikasa feels romantically). That being said, I also think it doesn’t actually matter whether or not Eren acknowledges romantic feelings for Mikasa. I just want him to acknowledge, and tell her, that he loves her and is grateful to her–because he does and is, regardless of whether that is familial or platonic or romantic, and the exact definition of that love doesn’t matter to the overall tragedy and beauty of their story. But acknowledging Mikasa’s personal romantic feelings would be a beautiful ending, imo, but that’s just my preference.