Is my tree dying?
This looks like a type of cherry tree. There may be several reasons for leaf drop. You may be dealing with a root stress issue such as too much or not enough moisture, soil compaction, etc. We also notice improper pruning (leaving stubs), cavaties in the main trunk (this can hold water and lead to decay), a large branch looks like it has a canker (right photo - this can deny moisture and nutrients to the tree, etc.
In general, cherry trees are not long lived. They can be susceptible to disease and insect problems when subject to the above issues. At this point all you can do is prune dead wood and prune damaged areas back to healthy tissue. If this is in the main trunk this is not possible. The best recommendation is to keep the tree watered during dry periods. Make sure mulch is no thicker than several inches and away from the trunk. If the canopy looks good in the spring and leafs out, all you can do is enjoy the tree. You may have to consider removal in the future.
Here is more on ornamental fruit trees and pruning https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/hgic/HGIC_Pubs/TreesandShrubs...