>>38512421Diagla is a complex design done right. Its colors easily reflect that of a diamon and it's shape allows it to maintain some feeling of being unique to go along with the steel typing. Remove the "armor" and it just looks weird. If you're truly determined about it, you could argue the cyan lines on his body represent timelines.
The key thing that truly makes Dialga work though is its silhouette. He works despite his details because his dinosaur + alien shape really helps him stand out among the other legendaries.