The term punishment kind of tricky in this context. Kazdin is a behaviorist writing a parenting book. In behaviorism, the term has a different meaning from it's typical use by parents.

In behaviorism, "positive" means adding something, and "negative" means taking something away. A reinforcement increases a behavior, a punishment decreases a behavior. So in behaviorism efficacy is built into the definition, if it does not decrease behavior then it's not a punishment.

In parenting, punishments are typically used incorrectly, overused, have bad side effects. And, most importantly, it's often not the best alternative because research has found better alternatives. Also, parents are reinforced to punish because they tend to be rewarded with short-term reinforcement, so it can be part of a vicious cycle. What parents consider a punishment might actually be reinforcement, for instance (1) yelling at your kid can make you look like a vanquished foe (2) if the kid can divert the parent into a predictable punishment mode, the parent might not follow through on something that the kid wanted to avoid even more.

If I recall correctly, Kazdin's does not tell parents to never use short-term grounding (or withdrawal of privilege), and that's a negative punishment in behaviorism. He says long-term grounding is no more effective and just causes resentment with no extra benefit.