What I've noticed common among a lot of Americans is a fear/inhibition of speaking the truth, mostly to not have a confrontation. I witnessed an example of this in a music performance of a teen rock band. In this performance, the band sucked overall. The guitarist didn't know what he was doing. But everybody (guardians, parents, teachers, friends) just keep saying, "Great performance brah, awesome shit, good going gu…
Everybody's enthusiastic at the performance, like you say.
At the next lesson, they review the recording. But then, they've been receiving that kind of critique at every lesson. You should hear the conductor let 'em have it at orchestra rehearsal. Because of this kind of dialog and close analysis, they also know exactly how well they're playing, immediately and intimately. Part of the goal is to teach kids how to engage in the critical dialog, and to be self-critiquing.
With the typical teen rock band, there is no adult involvement at all, other than fiscal.