This is correct. Fish should not smell fishy. But when you are in a fish environment like a market. There are all kinds of byproducts and liquid and fish blood everywhere. And that stuff can get pretty ripe quickly. And the smell of this stuff is strong. So thats usually what you smell not the actual fish filet. But if you have a fresh piece of fish and its sitting on ice. And you cut into it. And smell the meat. It will have no fishy odor. If it does. Its already bad.
On the other hand. There is nothing as delicious as truly fresh fish that has never been frozen. If you are looking at fish and you want to know if its fresh. Smell is not the way. Look at the eyes of the fish. They should be clear. If they are cloudy. The fish is getting old. Or hasn't been preserved properly. Frozen fish can be good also. Certain species are better to freeze than others. Oily fish such as a Mackerel and Salmon get a more pungent taste after they have been frozen but they are delicious fresh. Find fish with the head on it. This way you can tell for yourself. Almost guarantee you that the fish you buy as a filet from the supermarket has already been frozen. And then thawed for display. And its likely that it is a different species than they tell you. Same in a restaurant. This is why they come up with such elaborate recipes such as blackening and other heavy spices and preparations. They are hiding the bad taste or bland taste of the frozen or old fish. Fresh fish needs very little help. Just like a delicious grass fed steak on the grill. The flavor is in the meat.