It isn't the judgment per se that causes problems for the Ni dom so much as it is the inability to effectively process new data once a decision has been made. My experience with INFJs is minimal by comparison to my experience with INTJs, but I can give you examples of INTJs I know who reached their conclusions on the "correct" theory of nutrition, linguistics, exercise, politics, whatever 30+ years ago and steadfastly refuse to allow themselves to be influenced by new, contradictory information...
One of the huge advantages INFP actors have over INFJ actors is the fact they are, from a functional perspective, far more present-bound than future-bound. They don't jump on an Ni-train and act on automatic pilot, they remain open to the experience via Ne and Fi, both of which are present-oriented,
and as Meryl alluded to on ITAS, pray for acts of God or "accidents" to happen onstage/on set so that the acting takes place truly "in the moment." In other words, NFPs are far more comfortable improvising than NFJs. As those who work alongside INFP actors note, they are constantly changing line readings and characterizations to engender authenticity, both from an external perspective (so it looks real) and an internal one (so it feels real).
YouTube - Julius Caesar (1953) - Mark Antony speech
YouTube - Meryl Streep as Lindy Chamberlain