How to Gauge Whether a Foot Can Adapt to What It Is Asking It to Do

I take a more of a joint centric view on things or bone centric view which is I just look at the joints. So when you're looking at a foot, can it change shape? Can it move from a pronated to a supinated position? It doesn't have to be this huge change of shape, just the ability to move it in some way. And if I see a foot that just can't move and a lot of people will associate a stiff foot with a very super-native foot then there's an issue.