There are numerous words and phrases that can be used as synonyms for the phrase "not appreciating". Words like "disregarding", "disrespecting", "underestimating", "ignoring" and "begrudging" can be used to explain someone's lack of appreciation. Furthermore, phrases such as "failing to recognize the value of", "taking for granted", "overlooking" or "ungrateful" are also some of the synonyms that can be employed to describe a lack of appreciation. It is important to note that while these words may have similar meanings, they can be employed in different contexts to communicate distinct messages about someone's regard for something or someone.