Inbreeding isn't guaranteed to cause a problem. It increases risk yes but not 100% certain to cause a problem. Example if two cousins make a baby there is risk but not high risk.
eugenics just means selecting for desirable genes in a population, human or otherwise. It often gets a bad rap due to how its been implemented in the past (i.e. forced sterilization), but the concept of eugenics is not defined by its past implementation. Modern day examples of eugenics are things like polygenetic screening of IVF eggs.
