Even when we strip away the 3D and flatten the pie, interpretation challenges remain. The human eye isn’t good at ascribing quantitative value to two-dimensional space. Said more simply: pie charts are hard for people to read. When segments are close in size, it’s difficult (if not impossible) to tell which is bigger. When they aren’t close in size, the best you can do is determine that one is bigger than the other, but you can’t judge by how much. To get over this, you can add data labels as has been done here. But I’d still argue the visual isn’t worth the space it takes up.
