Time Travel to the past would not genuinely alter the future, because realistically time would not be altered in the past, but in the future.

In other words, time is constant, so going back in time would be going back in time in the future, therefore, only the future version of the past would be relevant, ERGO, the events in the past of the past would not be altered, only the past of the future event of traveling back in time would be changed.