The consensus is that Hamlet's delay, as it's often called, does lead to the concluding tragedy of Shakespeare's Hamlet. The delay itself, however, is not the tragic flaw. The tragic flaw is whatever personality trait makes Hamlet delay.
Some say he thinks too much, some say he is not capable of action that is not spontaneous, some say he is cowardly, some say he's "mad" or disturbed, some say he's depressed, some say he loves his mother in an abnormal way and that gets in the way of his revenge, etc. Some of these explanations certainly make more sense than others.
Of course, textual evidence should be used to support whatever theory one holds to.
By the way, some say Hamlet just uses good sense when he doesn't hastily kill the king of Scotland. This theory pretty much eliminates the presence of a tragic flaw in the play, which may be a possibility.
I'll cite one example. In Act 3.3.73-78 Hamlet, watching Claudius praying and all alone, unprotected, says in one instant that now he could do it, this is his chance. (Hamlet is now certain that the Ghost told him the truth about his father's assassination, so he knows that Claudius is guilty.) But in the next instant he says, no, he won't do it now because doing so would send Claudius to heaven, since he is in the process of confessing and his sins would thereby be forgiven.
This is a delay. Determining why he delays determines how one sees Hamlet and his tragic flaw. If you believe Hamlet is sincere, here, then Hamlet is playing God by trying to determine another human's salvation. That is not a good thing. And the result is a tragedy.
Others, however, view Hamlet as coming up with just another excuse for his inability to act, and these commentators see that inability to act as the problem, not Hamlet's attempt to condemn Claudius.
Whatever interpretation one arrives at, one thing is certain. Hamlet's assumption that Claudius is in the process of confessing is a mistake. Claudius never really does confess.