Kendrix wrote: I get its meant to spite this toxic purity complex thing but that's not the only possible reason people like her - she's ultimatel someone who had a short, unrealized, possibly doomed existence that was eventually cut short and couldn't attain that sort of normalcy excepts in the brief moments that she vaguely bonded with some of her peers.

I wouldn't say (outright) that Rei (every iteration) is a plot device by default. But on the most superficial she actually is. Which doesn't mean i share this opinion tbh. Rei is like you mentioned the core of Anno's personality. What if Anno's doesnt meant it that way but more specifically in the complete absence of social interactions. Just a thougth. So we get away from the cherry-picking "Rei is an otaku hate/love letter" or "She is a real human bean".

Consider this: (especially Nahash)
What if Anno intended the characters to be the superficial stereotypes (Shinji aka. whiner) but twisted the expectations by changing the context.

So changing the perspective it makes sense that every character gets a story arc. Shinjis arc is obvious. Asukas is resolved and Misato and basically everyone else. Think about the core of Anno's personality and what i said earlier: Rei isn't so much a hate letter for otakus but the anti-thesis of the puppet who wants to be a real boy (~err i mean girl). So Rei doesn't know these things - and in contrary to the Female Alien Teammate trope or the shy library girl (Rei actually reads books ... wat a twist) Rei is twisted into this new Archetype by completly stripping away all ties to humanity (except Eva). So her character arc revolves around becoming human and in the end doing the most altruistic thing possibly (in all iterations). She isn't a plot device but a self-insert from Anno himself to tackle and subvert even more tropes. And im pretty sure Rei-stereotypes existed even before Evangelion.

So was she meant to be this grosso modo imho? No i dont think so, but the context hints at it because it is vague and not clear.
Is there anything to talk about the interaction between Shinji and Rei? No, because Rei is either killed of or just the third wheel. Her character arc is closed and she has a tragic death. Just move on with her. She is dead in all iterations and brought with her nothing but pain and suffering (initiating third impact) and so on (like the puppet she is). But she gets on the redemption path by sacrificing herself several times by now and so on. She is a fully realized character by the time of her imminent death and has unlike others a complete arc (even cut short in the original).
Do i think like Kendrix that Asuka and Rei are symbolic dichotomies? No, because Asuka is so much more on both levels (superficial and in-depth). But she is cut short in the NME.

So overall: No, to get out of his cocoon Shinji doesnt have to give up Rei or face reality and be with Asuka. Because Mana, Sakura and Ritsuko are always around the corner. Rei isn't a doll (plot device or trap) but a puppet (knowing of her fate) who becomes a real girl. No strings attached. She is besides some other characters the only one who isnt romantically involved with anyone ... has a character arc and is realized by the creator of the show. Why cant we just let her rest. Rei is dead. Long live Rei.