dented ’dust covers’ on mid size or large concave cones can be inconsequential, they are still moving air, not perfectly, but a small fraction of what the coil/cone is still doing properly. The dust cap is covering the wire coil and the magnetic gap it moves in/out of.
dented is one thing, maybe the dog bumped his nose into it. Cracked, allowing dust, dry or moist air is another, avoid that. dust caps can be replaced.
dented tweeter, that’s bad, stay away.
