"Dopier" is an adjective used to describe someone who is unintelligent or lacking in common sense. It is always important to treat individuals with respect and kindness, so opting for more gentle synonyms when describing someone's intelligence may be preferable. Synonyms such as "foolish", "naive" or "gullible" focus more on a person's lack of wisdom rather than their intelligence level. Other alternatives such as "simple-minded", "slow-witted" or "dim" may also convey a similar meaning without being offensive. Remember, using words with sensitivity and empathy is crucial in fostering understanding and maintaining positive relationships with others.