aang choosing katara over the avatar state being seen as a touching display of his love for her is honestly one of the most egregious misreadings of the source text that exists in atla fandom and i really wish this interpretation would stop being touted in support of kat.aang when it is anything but favourable to either the ship or aang himself as a character.
aang having to let go of katara isn’t — in fact, logically cannot be — about having to let go of love, because there is no mention of having to do the same for sokka, toph, appa or momo. and even if we make the caveat that pathik was referring only to romantic love, it still can’t be true because we know that previous avatars have loved and been loved romantically without issue. roku, kyoshi and kuruk all had romantic partners, so there is no reason aang cannot. then it follows that aang needing to let go of katara specifically can only be because what he feels for her is not love — true, pure, selfless love — but attachment. aang’s choice isn’t actually for katara at all; it’s a choice for himself, because he doesn’t want to let go of her.
there’s a reason that aang’s grief over the air nomads gets brought up in this same episode, because it is inextricably intertwined with both his feelings for katara and his role as the avatar. after all, it was his being the avatar that led to the fire nation’s attack; it was his abandonment of that role out of fear that caused him to survive instead of being slaughtered with the rest of his people. the weight of his responsibility, and his failure to meet it, is the weight of his grief, and he cannot accept the former without coming to terms with the latter. this is a large part of why aang has latched onto katara, as a crutch to avoid having to face not only the reality of his loss, but the reality of who he is, and why he has to let her go in order to master the avatar state, the embodiment of what he once ran from.
the narrative framing of the guru episode makes it clear that the audience is meant to view aang’s choice as the wrong one. there’s pathik’s ominous warning — aang intentionally concealing the truth about not having mastered the avatar state from toph and sokka — and even iroh’s advice about choosing love over power (which gets thrown around a lot to defend the narrative dropping this plotline later on) is notably given without iroh being aware of the actual nuance of aang’s situation. with knowledge of the full context, it’s highly likely that iroh (a proponent of meeting your destiny on your own terms) would have said something entirely different.
it’s also narratively inaccurate to attribute the choice of the avatar state to being the choice of power, just as it is to attribute the choice of katara to that of love. within aang’s arc and the set up of his character, the avatar state does not represent power but actualization: the manifestation of who he truly is, and must become. it’s the equivalent of aragorn taking up the crown of gondor, simba returning to pride rock — a staple of the classic hero’s journey, where the protagonist fulfills his goal by facing what he does not want to face and accepting who the story needs him to be. if we apply the Want vs Need paradigm here, then katara is the Want while the avatar state is the Need.
the same arc is mirrored with zuko in the book 2 finale, drawing upon the two characters’ relationships as narrative foils. both zuko and aang choose wrong — choose the Want — and pay the price. then comes sozin’s comet and the agni kai, and the conflict of love vs power returns again with katara as its lynchpin — but this time, when zuko leaps in front of azula’s lightning, we know it’s the right choice because the story has established the choice of katara as the Need, as the completion of zuko’s actualization as a character. in aang’s arc, the choice of katara represents divergence, leading him further away from his destiny; in zuko’s arc, it’s a convergence, the re-alignment of who he was with who he’s destined to be.
and if the show had followed through with what had been initially set up, this moment would have happened simultaneously with aang letting go of katara, making peace with his grief and so earning the avatar state on his own terms in his fight against ozai — completing the reverse triangulation of the CoD plot. but instead aang’s side of this story thread is dropped entirely, fracturing the narrative symmetry between him and zuko, and his own character development in the process. and so, despite how hard both the show and the fandom have attempted to retroactively justify it, aang choosing katara over the avatar state is less a grand romantic gesture and far more an example of one of the show’s biggest narrative failures and frustrating wasted potential.