Let's agree that a normal driver without autopilot (ND) is mostly attentive, with occasional attention lapses (frequency depending on the individual).
That same normal driver according to MIT, is less attentive when using an autopilot system - let's call this autopilot distraction (AD).
However, the Autopilot system, despite its weaknesses, likely offers some extra safety benefit (ASB) - especially if it can somewhat counteract the attention lapses that a normal driver would have.
So the question becomes, does the autopilot's marginal benefit outweigh the autopilot distraction?
Is: ND > (ND - AD + ASB)?
However, determining this would be difficult without real-world testing. In the real world, the factor which matters most is whether accidents happen (kind of the Overall Survival of this experiment) - which is why testing the real-world accident rate is important - and is ultimately the important question.