What the others say plus, workshop papers are the lower end of the line. They usually have low novelty and contribution to the field and workshops are for networking and ideation. The whole process is less serious and a workshop publication does not count as major contribution to a PhD.

A good review not only shows weaknesses but also emphasizes strengths and give tips how to overcome weaknesses.

Overall a review is honest and if you feel not really ready for doing it, do it for the practice and tell the chairs your own doubts (there are usually ways to do so). You won't make any progress if you hesitate doing it.