I’m not sure I understand the distinction you are making here but I wouldn’t say it’s the only way to categorically identify mushrooms either. It is one tool among many, and one that is typically used with unfamiliar mushrooms, not those that a person is already familiar with.

Basically if you are not sure what you have it can help narrow down the possibilities. But typically if you are picking mushrooms to eat you are (or should be) already certain of what you have. I can’t think of a single scenario where spore prints would be the easiest way to distinguish similar edible and poisonous mushrooms. There are many other features that are more readily examined and spore prints are mainly for separating more distinct types of mushrooms from one another anyway.