It's not surprising that older writers and readers don't read younger writers as much, if at all. There is so much available now that just keeping up with work by writers one is already aware of can be a strain on time and finances for your average reader. Deliberately seeking out new writers requires a conscious effort.
On a pragmatic level, one would think many writers would attempt not-them protagonists, if by inclusion it might gain them new readers. If they're not comfortable writing the other, few can fault them for trying. Pushing boundaries and experimentation has brought some of the best work in genre.