There is no simple answer to this.
According to me; reservation is justified. but it needs changes. The main aim of reservation was "upliftment of the poor people". When the constitution was written, the poor were the scheduled castes and the scheduled tribes. So reservation was given to them. But now, they are not poor anymore. The law should be amended. Reservation should be given according to financial condition of the family instead of the caste or religion. In this way, the people who are still poor can get the benefit to make their standard of living better.