The phrase "think too little of" implies that someone is underestimating the value or importance of something or someone. There are several synonyms that can convey a similar meaning, such as undervalue, underestimate, belittle, disparage, diminish, and denigrate. Undervalue can be used to suggest that someone is not fully recognizing the worth or significance of a thing or person. Underestimate implies that someone is not giving enough credit to the potential or capabilities of a thing or person. Belittle, disparage, and denigrate suggest that someone is actively minimizing or insulting a thing or person. Diminish can be used to suggest that someone is downplaying the importance or impact of something.