We have been on 3 cruises, 3 different cruise lines. Met ship workers from Slovakia, Phillipines, Costa Rica, Romania, England, USA, Canada plus some other countries. Never heard that they exclude any countries.
However, you should know that, on the last cruise we were on, some workers had to work 8 straight months before getting any time off.
Very many Indians work on cruise ships and jobs range from ships crew to ships officers to passenger crew and staff. Many are waiters and work in the food and beverage dept including bar staff. I have also seen most of the security staff being Indian.