They're silly because they're Nosferatu rip-offs with all the subtlety of a herd of elephants and all the character of cardboard cutouts, shoved into a complex relationship with the Romulans that just doesn't make any sense at all. (They're downtrodden slaves from birth, yet capable of building and crewing that massive ship, not to mention blowing up the entire Romulan Senate without ever tipping off the Tal Shiar. Plus, if the planet of Remus is just a slave-mining hellhole, why would anyone ever mention it as relevant/central to the Romulan Empire? They'd've made more sense as a broader slave class spread around the empire including both Romulus and Remus rather than the primary inhabitants of a single slave operation which somehow rates interstellar recognition.) Being previously unknown has nothing to do with anything. Granted, there are other equally silly species in the franchise, and some even sillier than the Remans, but the idea that they're no worse than average is laughable. They're in the worst 10-20% easily.