Fair enough, though I would argue we do learn a lot about them organically, specifically through their relationships to other trolls, past actions they've done, and blink-and-you-miss-it moments in cutscenes. Their introduction scenes moreso set up the framework of the character, and a lot of them develop on that, though some remain somewhat static, but I blame them not getting enough screentime (which is fair due to the sudden influx of characters).