I am just 120 episodes into Naruto but I've been plagued by this for a while so whatever.
Is Naruto x Sasuke gay on purpose or gay on accident? I think the answer is weird mix of both. Naruto is a story for a teenage male demographic and WSJ manga are geared towards appealing to masculinity. Masculinity as a trait in men is often a performance for men. Men don't try to seek the approval of any other gender for their masculinity. Other genders, primarily women, are accessories to increase masculinity but that is not who has the final say that matters in terms of true masculinity because [deep sigh.......] we live in a patriarchy, you get the drill.
The existence of women as accessory means their opinions, thoughts, contributions are just as frivolous in the eyes of this masculinity performance and they therefore recede into the background. This, on top of general misogyny and patriarchal beliefs leads to women and anyone of any other gender to straight up vanish from the story. They are insignificant, therefore their relationship with the men are also insignificant.
Naruto's entire premise is built on outperforming masculinity against each other. The Shinobi world values power, only men and boys are allowed to be powerful because "girls are weak and don't have the same amount of drive to push themselves as the booooooysss doooo".
Naruto and Sasuke's bickering rivalry is at the center of it all. Combat and power is acknowledgement. The story is so, beautiful in how it doesn't even try to pretend to be bigger than this. Strength gives you power, agency, respect, love, anything a man can want, even the leadership over a whole village! Combat prowess and power are therefore the only means by which people, more specifically the boys and men of this show communicate.
Naruto wants to get stronger not to impress Sakura. No, no, she's obviously secondary, her affection is the prize. Naruto ACTUALLY wants to get stronger to beat Sasuke. Not just beat him, to get him to acknowledge his masculinity. This isn't a gay thing, this is just how guys interact irl. They put on a whole performance where they act like they feel nothing around their guy friends when you know you saw that dude acting very different with the girls and the gays and the theys.
BUT. But if Naruto(the show) was just this, the homosexual subtext underlying Naruto and Sasuke wouldn't exist. Nay. There is more. While all of this is accidental subconscious systematic things working to shape their relationship, there is a deeply intentional aspect as well.
Naruto and Sasuke's relationship is the only thing that matters. Their bond is deep, profound, they acknowledge each other and they are the reason they have each gained that ever-coveted power.
More importantly, the emotions, the gushy-mushy totally manly bro trust me feelings are only verbalized and acknowledge with one another. I've heard Kishimoto wrote this story to center around the ways in which these two support one another, guide one another. They are the emotional crux, the heart.
You perform masculinity for this one guy and one guy only, you feel anything real only with this guy. What do you get? ROMANTIC TENSION. Intentional or not, the extent of it can vary however much but this is how you do it. It doesn't matter if you didn't know the recipe to making cake crepe and accidentally made pancakes. You've got a fucking pancake. Naruto and Sasuke's relationship accidentally stumbled right into a romantic dynamic from the get-go. Idc about author intentionality and what the man and his editors have said (death of the author yada yada). The text of Naruto is just, this.