They don't need to change the structure of the show, it's fine the way it is. Steven's the viewpoint character, that means some things will happen of screen and sometimes that means missing things I would have liked to see but so what? It was Rebecca's choice to tell the story this way. And you not getting as much Lapis as you wanted doesn't mean the show mishandled or neglected her, for the longest time she was a tertiary character at best because she intentionally kept her distance because of her trauma, that was a believable portrayal of such a character. Of course they could have done more with Lapis if the show was about her but it's not.