One of the most common mistakes people make, both in real life and in creating fictional characters, is to confuse average differences with intrinsic differences. Take the sexes — are there differences between men and women (aside from the obvious anatomical ones)? If there are, they are on the average. For example, men are taller than women on the average, but there are short men and tall women. It is not an intrinsic difference between the two.
This is true of pretty much any groups of people, any populations. Even if we posit differences, they would be averages. This makes them essentially meaningless. We have to remember this both when creating fictional humans and when dealing with ones in our everyday lives. Do not judge according to some average. Do not assign certain characteristics to an entire population.
Tolkien was bothered later in his life by the fact that he had made his orcs intrinsically bad. He recognized the insurmountable difficulties this had presented, that it made them less than thinking creatures, creatures with souls (in whatever sense one wishes to use that term). Even if they were soulless animals, it is not really a good choice to make them all bad. That would be similar to those who claim all pit bulls are bad and dangerous.
So, not all goblins should be evil nor should all dwarfs be greedy. Maybe even dragons have their good sides (they do in my stories!). Nor is one human tribe or nation worse or better than another. Yes, there are average differences and these can be mentioned. Still, one runs into the occasional tall dwarf and the occasional muscular woman warrior, not to mention a few jumbo shrimp.