Your trees need the services of a certified arborist.  The dead limbs need to be removed and the canopies opened up to allow sunlight in.  It is common to have mature trees have dead branches.  Having them removed improved the health of your tree.  I personally have my mature maples 'cleaned up' by certified arborists every other year.  Once they have done their job, you will be pleased with the look of your trees.  They also will/can removed branches with poor junctions preventing them from breaking and tearing bark all the way down the trunk. Mature trees are a valuable part of the value of your property so taking care of them is worth the cost.  Go to this site and click on Find An Arborist.  Fill in your zip code when prompted and a list of certified arborists in your area will appear.  https://www.treesaregood.org/