ALT + rotate now duplicates objects instead of anchoring the opposite point

I don't recall that using the ALT key (or Option key on a Mac) ever did what you're saying. Alt/Option dragging has always been a way to make a copy of an object. Are you using the Rotate tool or are you rotating using the Bounding Box that appears when the regular selection tool is active? With the Rotate tool you can rotate around a chosen point by clicking on a point of an object (with the Rotate tool active in the Tool Panel) and then rotating the object around that chosen point. You can either drag from a point opposite the chosen point with the tool itself or you can double-click on the Rotate Tool and enter a value in degrees in the Rotate Tool dialog that appears.