As a fellow ex-ESL teacher, I wholly agree with your point.

But pretty much anyone who was ever a beginner at anything will understand how much feedback is vital to improvement. After all, how are you supposed to know you're doing better?

In fact, research shows that "academic feedback is more strongly and consistently related to achievement than any other teaching behaviour" on top of that it is consistent regardless of grade, socioeconomic status, race, or setting.

(Bellon, J.J., Bellon, E.C. & Blank, M.A. (1991) Teaching from a Research Knowledge Base: a Development and Renewal Process. Facsimile edition. Prentice Hall, New Jersey, USA. )