From Wikipedia: Elegance is a synonym for beauty that has come to acquire the additional connotations of unusual effectiveness and simplicity. Elegant things exhibit refined grace and dignified propriety.
Elegance is in the eye of the beholder
Some people find Saito-sensei's aikido as old fashioned and thus boring, but to me it is one of the most elegant styles due to it's naturalness, simplicity, straightforwardness and devastating effectiveness. Even if I hadn't felt Saito-sensei's techniques and just watched many of his videos, you can "feel" how effective it is and his teachings can be reproduced on the mat to validate their effectiveness.
For some teachers that have newer and modern styles, although their techniques look more sophisticated and refined, their effectiveness now comes into question.