Issue after oracle database 11g to oracle 12.2 migration facing major performance issue?

We are done recently database migration oracle 11g to oracle 12.2c. After migration facing huge performance issue in oracle 12.2c database. But if we set alter session set optimizer_features_enable=""; then performance fast. Here i have doubt why it's taking so much time higher version (optimizer_features_enable=" What we need to check for this parameter. Please suggest us?