The phrase 'pick holes in' refers to the act of finding fault or flaws in an argument or idea. There are several synonyms that can be used instead of this phrase, such as nitpick, criticize, scrutinize, and fault-find. Nitpick is used to describe a person who is very critical and focused on small details. Criticize is a more general term and can be used to describe any form of criticism. Scrutinize is similar to pick holes in but suggests a more thorough examination of the subject. Fault-find implies a more negative or irritating form of criticism, often done in a constant manner. Using these synonyms can add variety and nuance to your communication.