Saying Banana Fish is a yaoi isn't "watering down" the story at all, if you think that the word yaoi means fetishizing gay men, then you are inherently homophobic. 

Yaoi, while originally named as an umbrella term for parodies of works to depict homoerotic relationships among men, the connotations of the word have long since changed since it was coined decades ago. Boys Love, Yaoi and Shonen Ai can all be used interchangeably. 

As such, any story that involves love between two men, can be called a yaoi/BL/Shonen Ai, the word choice is all the same. Unfortunately, due to homophobic depictions and stigma around gay men, the meaning of the word has been bastardized. It's like calling a straight romance anime a "hentai". Just as Yuri isn't necessarily smut, Yaoi isn't either. Like no, it's not fetishizing gay men to ship two male characters, no one would ever say that about straight ships, anyone saying that just views queer men as sexual beings incapable of feeling love like a human being. 

As for the author denying that Ash and Eiji were in a romantic relationship, that viewpoint is very fair, however they have never once claimed that they were straight men. To kinda assume that anyone's sexuality "by default" has to be straight unless explicitly mentioned is rooted in homophobia. All the author said was "They shared a deep bond between their souls that can't be defined with words" (Gayest shi I ever heard in my life omg, Ash and Eiji are so cute 🥹🥹). 

Now, to put forward the fact that the story hints at many gay themes, some of which were very explicitly stated, it's not crazy to think that Banana Fish is a story where male homosexuality is a main part of the story. 

While Ash and Eiji aren't explicitly dating or in a relationship, there are countless moments (I mean, basically every moment they're on screen 😭😭) that heavily hints they're not just a straight male platonic friendship, and I think most would agree that the friendship isn't one that a straight man would share with another straight man. It's completely fair to think that Ash and Eiji are gay men who loved each other, but never had the chance to be in a relationship with each other, and this lines up well with the story as well, considering the ending of the series. Banana fish is a tragic story of an unfulfilled love. Calling it a "doomed yaoi" also is completely fair. Not to mention, Banana Fish inspired the genre of Yaoi/BL very heavily in the coming decades.

So, calling Banana Fish a yaoi is a completely valid viewpoint that fans can have, and thinking that the word yaoi somehow waters down the story because any animanga depictions of gay men are nothing but smut is rooted in homophobia. As a bi man, I personally crown Banana Fish as the best and most influential yaoi ever created. Let people enjoy things 👍

Being Afraid of the Word 'Yaoi' and Thinking It's Nothing But Smut Is Homophobic Btw