You made a great observation here. The way you are analyzing the sentence and thinking about it is going to help you master English and use it very well. It is a waste of time to use too many verbs in one sentence! But I am only kidding; the truth is that in this sentence the word 'waste' is being used as a noun.
The verb in this sentence is 'to be' and it is conjugated as the word 'is'.
The word 'waste' refers to something that wastes time.
Example: An empty forum is a waste of time.
Important: Add the article 'a' to make the sentence better: It is a waste of time.
Student or Learner