> Are you saying that it's bad if my coffee beans are glistening with oil?
It isn't inherently bad, but it's usually a sign of more mass produced coffee. It's easier to roast coffee like that because it all tastes pretty much the same which is good if you need to make the same coffee for thousands of different locations. And some people enjoy the carbonic taste of coffee like that.
More lightly roasted coffees will have big differences in flavour that's not really possible to control for on a mass scale I don't think. Especially between origins and varieties.