IMO, the principles have always been clear. It's their application that raises doubts. I mean, every Christian understands we don't celebrate Christmas, and no Christian has a problem with covering his mouth when yawning, even if they both originate with false religion, because those are extremes.
It's more difficult to understand, and to some degree arbitrary, why some practices that have lost their religious meaning are acceptable while others are not. Wedding rings are ok but toasting is not (well, until now). Piñatas are acceptable but throwing rice to the newlyweds is not. What is the reasoning? I don't know.
Some decades ago we were unbearably strict. We were a stick in the mud, looking at everything with suspicion and finding traces of false religion everywhere. The same as a child matures until he becomes a man, our organization is constantly maturing and learning to apply Bible principles better. When I went to pioneer school at 16 my mind exploded with the chapter about Bible principles. I remember chess being avoided by Witnesses because it was a war game. I remember articles quoting Christendom fundamentalists saying rock was Satanic and an article quoting an idiot claiming E.T. was a parody of Jesus. As an organization we have come a long way from then. We recently understood that we cannot tell Jehovah who should be saved and who should. We understood a more logical, loving and Christ-like way of treating those who were removed from the congregation. We understood beards. I'm sure our application of Bible principles will continue to be refined in the future.