The point of your sense of taste is to get you to eat the things you need. Your tongue must be able to detect whatever those things are.
Some such substances occur across a broad range of foods, or in varieties that differ from each other in ways that don't really matter to your digestive system, and you can pick them up and consider them to be a flavor common to those foods.
Some are unique. You can pick those up too.
In either case, your perception of the same taste will vary according to the current state of your nutrition. Steven Callahan noted that, when he was lost at sea and food was scarce, fish eyes tasted significantly better than the rest of the fish. That is because they contain important nutrients, which your tongue can detect, but which you don't ordinarily care about. You start to care as you develop deficiencies.
A model of a small number of "basic flavors" doesn't even allow for this phenomenon to exist. It is fundamentally misguided.