this is really rambly but whatever im just talking
harrenhal bath scene for e.g. it's a confessional and a baptism. jaime reveals his deepest secret to brienne, she sits quietly and listens. it's a kind of cleansing: she knows everything else, but she doesn't know this. he's entirely bare before her, both figuratively and literally, and at the end he's effectively reborn in Brienne's arms, internally insisting upon his true name. it's more like a return to and a reclamation of that name, after having been known so long as 'kingslayer'.
and it goes w/o saying that GRRM is expressing here a pretty catholic sentiment - one achieved through confession and atonement:
[On Jaime] I want there to be a possibility of redemption for us, because we all do terrible things. We should be able to be forgiven. Because if there is no possibility of redemption, what’s the answer then? X
and like GRRM isn't exactly shy about highlighting the contradictions and hypocrisies of the FO7, knighthood and the KG - which ftr are tied up in each other. knighthood is sworn to the Seven, as a part of Andal culture that was carried over with the invasion, and KG sprouts from the ideals of knighthood, even whilst corrupting them further.
and I think the point in Jaime and Brienne's story is that the core tenets of knighthood do mean something, just as even a lapsed Catholic might appreciate the core tenets of loving one's neighbour etc, if not the religious practise. to be caught up in the terms and conditions is to lose yourself in what it's all meant to mean. Brienne once judged Jaime harshly according to the rules, but found greater understanding of him, herself, and the world around them by opening her mind to the nuance, and trusting in her own understanding. it's not that knighthood is a fundamentally corrupt concept, but that true knighthood is about understanding it as a broader worldview of care for those weaker than yourself, rather than a set of rules, or a status symbol.
i think FO7 (particularly following HOTD lol) often gets slated as the worst faith bc it so resembles western christianity and all its associations, and the zealots (and what they do to characters like Cersei, Lancel etc) represent the very worst of that faith. the other faiths have something more mystical and formless about them: the weirwoods are tied up with the magical core of westeros, r'hollorism is clearly fucking onto something etc. and they're more appealing in that sense.
but I don't think the FO7 is portrayed entirely negatively! the way our FO7 characters follow and ponder the Seven as they relate to themselves is a really interesting device for introspection. Jaime for example has always seen himself strictly as the Warrior - he doesn't care all that much for the FO7 more broadly, but this is the prism he's understood himself through since childhood - he's the perfect archetype. likewise, it's the prism through which he once understood Cersei (i.e. as the Maiden), yet this led instead to a reduced understanding of Cersei as an individual. Brienne meanwhile feels apart from both the Maiden and the Warrior - she fits neither. both in a sense reduce themselves in how they do or do not relate to the Seven.
but without getting into JB and gender again (cos I will), their stories are more a contemplation on the fluidity of the Seven. it's said repeatedly in the story that the Seven are one, and so it then seems quite contradictory that characters should asign themselves to one and not the others. neither Jaime nor Brienne are simply the Warrior or the Maiden, they can be both each to the other: there's a kind of synchronicity in this, in that neither is solely the protector, neither is solely the protected. through the true ideals knighthood, they are both to each other. what seems rigid as a concept is actually one that can be interpreted more freely, and reveal new facets of the self rather than shut them down.
anyway so as i say this is rambly but i guess my broader point is that JB are sort of an exploration of how faith does not have to be about shutting down parts of ourselves, limiting our worldview, and striving to live untainted, but forgiving and finding ourselves and each other. it feels familiar to me as a lapsed catholic MYSELF: a deep scepticism and discomfort with the rigid dichotomies that send you fleeing from it in the first place, but a sort of new inquisitiveness and warmth one feels when considering its core tenets on one's own terms.
who fucking knows what exactly GRRM's relationship with catholicism is (idk even what mine is), but I think through jaime and brienne you maybe get to see some of the better things he took from it, i.e. forgiveness, introspection, generosity of spirit etc. like if you do away with all the corruption and misinterpretation and you sit with just the core, I guess you are left with what Brienne strives for in AFFC. she is not fighting for any individual or institution, but purely what she has taken away from knighthood, and what she believes to be right and good. and Jaime, once disillusioned by the rigidity of it all, is inspired by precisely that