Will Byers & Frodo Baggins, the unusual protagonists
Lots of people make parallels between Harry Potter and Will Byers, and I'll always be sad (and mad) the writers of ST didn't explore the whole Vecna/Will connection similar to Voldemort/Harry, but I also think it's interesting to compare Stranger Things with Lord of the Rings (also the show made multiple references to it, in s1 with Mirkwood, then with Eddie in s4, comparing the Upside Down to Mordor, and by extension Vecna to Sauron).
Both Frodo and Will portray a different type of male protagonist, one who leads with their emotions, inner moral code and empathy rather than emotionless logic, display of strength or physical dominance, and/or charisma/humour.
They also both faced similar criticism: they are said to be too soft, too "boring", whiny, useless even, precisely because they're not the usual male protagonist people are used to see and therefore expect.
Frodo & Will carry a lot of emotional weight to the story. Their suffering, resilience and unwillingness to succumb to the darkness are a crucial part to help defeat the antagonist, but also to send a powerful message to the audience: no matter the pain, no matter the hardship, light will defeat darkness, love will triumph over hatred, the good wins over evil. Strength doesn't always come from where you expect it, as a simple Hobbit or a quiet, gentle boy can save the world in their own unique way.
And yet, their pain is often dismissed, mocked or downplayed.
Part of it is because it leans more on psychological pain, therefore is more internal than external, but also because of how people tend to admire, or reward, certain types of pain more than others: a hero who physically fights against a monster and gets hurt or dies will be more remembered and admired than a man who internally battled against an evil force trying to take control of them, or a man who decides to spare an enemy and choose kindness (it can depend of the context and media, obviously, but it's still a pattern I noticed).
Men like Hopper or Steve are usually more respected, admired and remembered because they are pro-active, embodies typical masculine traits and behaviours, and physically fights against the monsters and/or antagonists. (Not to say it's a negative thing in itself, btw, I find both Steve and Hopper to be interesting character, and Steve's character actually challenges masculinity in its own way, but that's another topic). In LOTR, Aragorn, Boromir, Legolas, or even Gandalf (who physically fights with magic) also "stole the spotlight" from Frodo, to some degree.
Even if Frodo and Will participate in defeating the antagonist, they need protection. They are not the strongest physically, they need the help of others. They also don't jump into action or into a fight, they use their head or hide/run away.
In a way, Frodo and Will have typical "feminine" traits (or what we socially learn to associate with women and femininity), sometimes fit into tropes typically reserved for female characters, and it makes some people uncomfortable, whether consciously or not.
They're both typed as INFP ("mediators who are poetic, kind, and altruistic people, always eager to help a good cause"), a type usually given to female characters, at least in shonen and action-oriented shows, to counter-balance the male protagonist.
I also think the way people treat Eleven and Will is very telling: El is overall popular and well-liked. She is a woman and suffers from misogynistic writing and misogyny from some part of the fandom/GA, but she is portrayed as physically (and mentally) strong, despite the horrible traumas and harship in her life. She cries a lot, she expresses her emotions (as she should btw), and she is allowed to without people calling her whiny or annoying. It's part of her character, both her emotions and actions.
Will on the other hand, doesn't cry on screen as often, yet when he does cry or express emotions related to the pain or trauma he faced, he isn't given the same grace as El, and I think it really comes down to the fact El is a girl and Will is a boy (and boys don't cry, right?). Every human being, regardless of genders, have emotions, and should be able to express them. But fiction reflects society, and the way we respond to fiction is also affected by social norms and patriarchy.
A boy who suffers must not show he's suffering, and must not show he's battling with the consequences of his trauma. A girl can, but she is often reduced to her emotions, patronised because of it, or used as a plot device so the male characters can grow thanks to her. Nobody truly wins in this.
What made Will more popular to the GA was his fight against the Demogorgons in the Sorcerer episode after he unlocks his power in season 5, and when we saw flashbacks of him surviving in the Upside Down (+ when he used a gun). Again, typical stuff that we reward in boys and expect a man to do, especially as a main character in fiction.
But as soon as Will went back to his "soft" self (which ultimately is who he truly is, not some kind of hot sorcerer on steroids), he was yet again disliked and back to being categorised as annoying and whiny.
Will & Mike also parallel Frodo & Sam.
I mean, Mike the Brave and Sam the Brave? C'mon. They're both the reasons Will and Frodo don't succum to the dark side (Mike helps Will from getting completely possessed by the Mind Flayer + unlocking his power and by extension, fully accepting himself; Sam stops Frodo from getting too influenced by the Ring). Both Mike and Sam are loyal friends who help Will and Frodo to stay true to themselves, to remember their root.
Their friendship are the core of the story, and both have an insane amount of genuine chemistry and love (regardless if you see it platonically or romantically).
I think there's beauty in quiet, gentle resilient characters, and Will & Frodo embody it in a very special way that is so very needed, especially for boys who don't fit in the male archetype and will feel seen thanks to those characters.
