Ninette de Valois — Irish Dancer born on June 06, 1898, died on March 08, 2001

Dame Ninette de Valois OM CH DBE was an Irish-born British dancer, teacher, choreographer and director of classical ballet. Most notably, she danced professionally with Serge Diaghilev's Ballets Russes, later establishing The Royal Ballet, one of the foremost ballet companies of the 20th century and one of the leading ballet companies in the world today. She also established the Birmingham Royal Ballet and Royal Ballet School. She is widely regarded as one of the most influential figures in the history of ballet and as the "godmother" of English ballet... (wikipedia)

It's either not good enough and dies altogether, or it develops.
Oh yes, technique has definitely advanced. But you never advance without losing something en passant, and you lose it because you're paying so much attention to the new thing.
And then you have the classical ballerinas, they're like sopranos. Applied to the dance.
Classical ballet will never die.
Exactly the same with dancing, you can't dance until you've learnt steps, the things your feet can do.