The caste system was a bad thing.
It does not allow a person to pursue a profession of his/her choice. If a weaver is good at farming and wants to do farming, he will be opposed by people of his caste and other castes.
Marriages in the same caste and relations increase the chances of genetic disorders. In India there are some castes with very less people left in their community. So, in those castes, marriages among first/second cousins are very common. Thus making more prone to genetic disorders
Caste system divides us. It makes some people superior and some people inferior. This prejudice is dangerous for any nation. Now reservation system has taken place of caste system in independent India which will further divide our society.