NPS is first and foremost a marketing tool for Bain & Co to sell expensive consultants and def not "the one question to ask".
Several marketing scholars have pointed out the psychometrically undesirable properties of the metric and there is conflicting evidence on e.g. the metric's predictive validity, e.g. in relation to company success
(All in all that old HBR marketing article contains very little details to back up the claim that it is a good and valid metric.)
If you can go with behavioural outcomes for measuring success, e.g. purchases, I think that that will always be more powerful than what a user says in a survey.
And if you can then causally link (e.g. through experiment) something you can influence (e.g. some dimension of "UX) to that outcome you actually have a quite good decision tool too.
NPS does not provide that.