One must be reasonably certain that they understand what is being said before they can genuinely agree, disagree, or suspend judgement. Suspension itself is also a type of criticism - it is the stance of not being convinced of one position or the other. only after proper effort towards understanding is “I don’t understand” a valid criticism.
How to read a book by Mortimer Jerome Adler, Charles Van Doren Criticizing a Book Fairly Avoiding Contentiousness