when playing the fontaine AQ i didn't personally interpret furina's arc as being exposed as a fake since she and focalors are still elements of a single being, despite being independent in the consciousness and personalities, and thus furina was still by all rights the hydro archon. capitano and focalors/furina do share some similarities individually (though their dynamics with mavuika and neuvillette respectively could not be more different), but they can only be so similar when natlan was just overall written better. however, i completely agree about how heartbroken everyone appears to be over capitano's sacrifice compared to previous deaths, and more so than focalors i would compare the response to signora's death, which was legitimately just poorly written and timed for shock and wasted an entire character.

capitano's death seems to be suddenly dredging up disappointment about underdeveloped/underutilized harbingers when so far he, arlecchino, and dottore have been utilized the Best in regards to their respective roles, while signora and scaramouche were wasted and childe continues to just be a guy who flails around like a wounded osprey, as he should. capitano differs from the rest because his role is attached to mavuika and that is a level of importance that people didn't want her to have. you've unfortunately hit the nail on the head that a woman's sacrifice for a male protagonist's development is simply the rightful way of things, but when inverted, that principle is cruel and unjust and bad writing lmao