Black holes are visible, but emit less radiation than the cosmic microwave background. It's therefore possible to take a picture of one if you have very very sensitive instruments.

However, the article is talking about taking a picture of a shadow, which isn't really the same thing. Yes, it's impressive, but it really should read something like "First Picture of Black Hole's Direct Effects". We've already taken pictures of gravitational lensing caused by black holes, so we've seen some indirect effects.