I am sorry for this delayed reply to your gardening question. The spring rush has brought a deluge of questions and we are working hard to catch up!
Based on your description of the tree I am not sure whether it has a problem or not. Old trees often are in such a condition. The air plants are not a problem at all. The older rotting branches may need to be pruned off but Magnolias are native and live a long time in such conditions. My gut feeling is that the tree is fine and perhaps a little cleaning up pruning here and there is in order.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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