We judge people all the time. We make determinations about their thoughts, their feelings, their actions and etc. That's how relationships function. Perhaps a better, more precise word would be judgmental. If we are judgmental about people, we are looking at their "flaws" and if we cannot accept people for who and what they are, then we do not have time to love them.
When we judge people we strip away their unique characteristics and view them based on what we are judging them on. For example, if someone is on public assistance people may judge them by saying the person is lazy. However, in reality the person may be ill or injured. When people judge, they only look at negative aspects without considering other possibilities.
As post #2 notes, literature is replete with examples of this foible in human nature. With Wuthering Heights as yet another example, no one in the novel seems to understand why Catherine loves Heathcliff because they cannot reach beyond his wildness of appearance and demeanor.
Studies have shown that people make judgments about others within the first 15 minutes of meeting them, and 75% of a job interview is determined by the impression that the person makes upon the interviewer. People may not be able to judge a person by the proverbial cover, but they certainly try. And, then, they often dismiss them for some flaw in their apparent personality, etc.
I think that what this means is that all we do when we judge people is to look for their faults. We spend all our time looking at them and trying to think about what is wrong with them. If we would stop doing that, we would be able to have the time to look at them with more compassion and understanding. We would be able to look for their good traits rather than their bad traits. Then we would have time to love them.