If it was an addon, it is definitely not possible now. Classic is a fork of retail. The engine, macros, and vast majority of the API are the same.
I think what you're looking for may be the "click-to-move" option in the Interface Options, which when used on objects or interactive NPCs, your character moves to them then interacts. I don't recall it working on spells, but I believe it does run up to an enemy to begin auto attacking.
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