I am not an expert on mending old quilts but I had two old family quilts that needed some mending. The tops were pieced by my paternal grandmother in the late 1960s/ early 1970s. My mother and my youngest sister quilted them for me (not the best quilting jobs but they did it) while I was in college. I decided to simple sew new fabric pieces over the torn/ frayed ones rather than removing the old pieces. In some areas I simple reinforced weak fabric with embroidery.
The first quilt was an album quilt with names (family and friends)/ places embroidered in place. I used this old shirt fabric as a substitute in this block. Wish I had taken an after photo.
I used an old denim striped shirt fabric for the repair in this block (lower right). Failed to take a before photo of this block.This photo shows where I embroidered some weak areas to strengthen them.
These next two (first is before, second the after). Sorry the orientation isn't the same.
Another one showing areas reinforced by embroidery.