I agree with you. I want to SEE more with Jonathan. One of my fav scenes with him was in s1 when he went to see his dad about Will. THAT was showing, not just telling. & I get it, like the kids are the draw and the show only has so much time, but they did decide to have this many characters. It's only fair to treat each one right. As screen time goes, he didn't get much, and most of it was spent on a relationship, which is great, but I want to see more. Please let next season have more!!
That scene with Lonnie in s1 is so crucial to understanding Jonathan and it’s a perfect example of showing, not telling. You get so much of their past history, and it’s clear that Lonnie used to physically abuse him, but you don’t get it through exposition. You get why the trust issues are there for him, but also how much he struggled against and made a choice to not be anything like his father. Those same trust issues were just relegated to a jokey line as part of a rom-com-ish scene in s2. Why would you just play that for humor after what you’ve established in s1? It’s a weird writing choice.
I mean the reference in s2 we get to Lonnie and what Will and Jonathan truly experienced is that incredible castle byers monologue–how they built it when Lonnie left, and they were both sick for a week afterwards. That’s pretty heartbreaking. And that’s the Byers family–they have heartbreaking things happen and keep going. And Lonnie’s bullying and abuse is an important context for the kind of bullying Will is experiencing and how Jonathan and Joyce react to it. It just feels like there’s still a lot to explore there, and not sure why the writers wouldn’t want to. Also, if you are going to bring Billy in and show how he also experienced abuse, but has become a racist and abusive himself, then land the contrast: Jonathan and Will grew up with abuse and precisely did not become like their father. But they sorta dropped the Jonathan contrast part of this, and just made his trust issues a punchline.