Everyone who reads a book is going to look at it from a different perspective, so this is really an opinion-based question. Yet this book is designed to make you question everything you took for granted. It is a personal journey. Therefore, the ending is appropriate. The reader is still left questioning.
The book begins with a prologue, so we already know how it will end in some ways.
The trouble began long before June 9, 1976, when I first became aware of it, but June 9 is the day I remember. (p. 12)
By telling the reader that there is trouble that began long before, and then describing the river incident, the reader knows that the past and present are going to be connected.
It is my belief that the ending of Kindred is meant to make you question several important points. Since the book's focus is on societal issues, the major question should be one of how society treats and accepts people who don't fit the mold. The main character has to find ways to survive in a society that has very different expectations than she is accustomed to. This is an issue that everyone faces at some point in their life. Do you march to the beat of your drum or quietly slip into society's mold?