I don't actually care what the Duffers intend or whatever they're doing lol, my canon will always be that Steve has adhd and Robin is autistic.
Steve is said to be "dumb" and struggle with school, but we only have two concrete examples of his academic struggles to go off of. I can't remember the subject, but in Season 1 Nancy has some test to study for and Steve offers to help her and she replies with "you failed his class" and Steve corrects her by saying he got a C-. Anyway, our only other concrete example of Steve's academic performance is when Nancy is helping him with a poorly written essay and I want to leap through my screen every time I watch that scene because the problem she points out to him his structural. He jumps to making a metaphor and drawing symbolism between fighting in a war and basketball that he can't articulate in a way that she can follow.
Along with needing help organizing his thoughts Steve has always been very tactile and fidgety, but the really interesting thing for me each season since Robin's introduction has been the way they've directed certain shots and scenes to show us that these two characters match each other. Steve was much more relaxed and less preppy and buttoned up in season three, not just in costume but in physicality as well. He and Robin sprawl. They take up space. They're always touching or playing with something. And I just love the thought of Steve unconsciously finding someone he doesn't have to mask as much with. To the viewer looking in their energy is supposed to be silly and chaotic for laughs but anyone with a chaotic brain that doesn't march to the tune it's supposed to knows, when you find your people that's a beautiful thing and the way you can amp each other up is one of the best feelings in the world. Robin has niche interests, talks fast, and struggles with social cues. The show has gone out of its way now in both season 4 & season 5 to make these jokes about her mother pointing out her flaws, all of which are spectrum coded.
So yeah, this will always be my truth for them.