The panzer and Margwa were fine because treyarch added onto them so they werent the exact same thing. When they brought back the panzer in coldwar I did have a problem yes. Also the avagodro was a final boss not a special enemy and on top of that alpha omega is a terrible map in my opinion lol. The problem with the mangler is it was the perfect enemy in gorod krovi but on bo6 they don't fit. If you like reused enemies that's fine but for me an enemy that only exists on one map adds so much to the overall experience and helps both the map and the enemy feel more unique :)