In many ways this is symptomatic of larger trends in society and managerial culture of looking for ways to measure things rather than confronting the messy subjective non-measurable reality.
The only time we'll get a true counterfactual is when a competitor arises who can meet Amazon's very high bar for logistic excellence but can offer a more appealing interaction, and then Amazon retail will die off without anyone understanding how or why it happened.
But I'm close. My purchases through them are down probably somewhere around 80%. My girlfriend never really used Amazon and doesn't see the appeal at all - telling someone "it used to be good" makes you wonder what you're doing.
Even AWS has burned me and clients enough times that we pretty much don't use them anymore - an idea that was unthinkable a decade ago.
The other thing is that the more they burn this goodwill the more they'll be tempted to increase ad revenue, and the more the goodwill will disappear.