The phrase "fail to see" is a commonly used expression that means being unable to understand or perceive something. There are several synonyms that can be used to convey a similar meaning. One alternative could be "overlook", which suggests missing something due to lack of attention or awareness. Another synonym is "misapprehend", indicating a failure to grasp or comprehend an idea or situation accurately. Additionally, "disregard" implies intentionally ignoring or paying no attention to something. "Neglect" is another word that can replace "fail to see", indicating a failure to recognize or address something important. These synonyms help to convey the idea of a lack of understanding or perception in various contexts.