The whole point of a chart is at-a-glance understanding of numbers and stats that would normally take a more careful once-over.

And the whole point of a pie chart is to use one thing -- the size of a slice -- to represent a single datum.

A 3d pie chart muddles both of those things for form-over-function reasons. How is this even contentious? Pie charts are notoriously bad anyway, especially if there's not a huge difference between the data points. This makes them notably worse.