Television has gotten a lot better since the 90s, it's really better than what's in theaters right now. Except for broadcast television, most of it is still awful with a few exceptions. Most of those shows have diverse casts and they help make the world of the show feel more realistic. The world is actually fairly diverse if you leave your house, it makes sense that media would try to recreate reality to some degree.That's like saying an all straight Trek - all the ones we've had in the past - were Three's Company in space.
Diversity in no way inhibits good storytelling.