See, I don't understand this line of thought at all. Sci-Fi has just as many recognizable archetypes as fantasy does -- or just as few, depending on how you view it. Why should there be classes in Medieval Funtime Land but not Future Funtime Land, or vice versa? The argument doe not hold up to any sort of scrutiny.I think with bounded accuracy, a 5E sci-fi system could work, but it wouldn't be my preference. Any sort of class system and especially the skill system would need a major overhaul.