I think that often the secular world looks at these portrayals of the Frum world (whether it be Fiddler on the Roof, Chaim Potok, or something else) very differently than the Frum world does.
That is because the secular world is starting out with either no knowledge or incorrect knowledge of the Frum world. They are also usually starting out with a very negative impression of the Frum world.
So they view these portrayals as positive since they are more positive than their initial impressions.
However, the Frum world who knows what the Frum world is about realizes that these are in fact negative portrayals of the Frum world.
Additionally, there are things that someone secular would not realize are problematic. For example, the mixed dancing in Fiddler on the Roof and the way the Rabbi is portrayed as an idiot who can’t figure out why it should be a problem.