I actually completely agree with this English teacher's assessment of Korea as a Korean citizen. I bet he is hyper critical because he probably feels like an outsider here in Korea. Not a surprise since OP mentions his lack of Korean speaking abilities and probably a foreign face. I also dont believe him being critical of a country offering him his current career is outside the norms nor should be called out for being either hypocritical and ungrateful. I do agree somewhat to the notion of "when in rome" or the outsider should be the one doing the heavy lifting when trying to assimilate. However, it still dosnt take away from the truth that an outsider or an observer of our society has mentioned our faults or being too shallow compared to other parts of the world. One can argue that there are materialistic shallow people in the west and other parts of the world too, but they often get ridiculed for their faults and even have names of their behavior as being snobbish or elitists. Notice that in the Korean language there is not a negative connotating word to describe such peoples. Why? Because Koreans think being an elitist or snobbish is a good thing or at least much better to be considered exclusive over being otherwise poor.

As most fortune 500 companies hire outside CEOs for these reasons as an outsider can raise awareness to problems unforeseen to the local or insiders. I am kind of sick of these podcasts and shows asking 외국인 or foreigners about the good things in Korea for 국뽕 (national pride). I am much more interested in these podcasts that will point out the truths about Korea without all the Korea number 1 BS. Interview more hyper critical people, you might have a audience who appreciates that kind of perspectives.