Indian management has failed to fulfill its responsibilities. KL Rahul and Ashwin have consistently played poorly. While KL Rahul played well in a few matches, Ashwin was a complete flop in the World Cup. Although India has adequate replacements, they have given Ashwin a chance in every match. However, India failed to qualify for the World Cup finals. We will probably see some changes in the Indian squad in the upcomming series after the World Cup.
I will not blame Ashwin much. Australian pitches are not very supportive of spin, and on top of that Ashwin himself has a poor record outside India. But in general, the Indian spinners had a poor outing in Australia, be it Axar or Ashwin. I don't think that any other spinner would have performed better than Ashwin. But the case of KL Rahul is quite different. He was a burden for India, with a number of younger players waiting in the bench for the lack of opportunity. Time has come for a complete revamp of the team.
Australian pitches support wristy spinners and India did have one (Yuzvendra Chahal) but Rahul and Rohit were more eager to play Ashwin and Axar because they can bat. Just look at the number of wickets these guys took in this world cup. Furthermore Ashwin was lazy on the field. The openers are a burden to Indian side the problem is that you cannot drop both captain and vice captain. That is why now BCCI has decided to keep Hardik Pandya as the captain of T20 squad for the long term and have asked Rohit whether he would like to play in T20 matches the same goes for Virat Kohli too.