Since the OP's post doesn't posit that anything would necessarily change other than us talking to our younger selves, I don't think it's necessary to assume that anything we do to alter our past is automatically doomed to failure. Yes, maybe it stirs up the quantum foam sufficiently to randomize the numbers differently but we don't know that quantum physics works that way since we have no practical experience with time travel. It's a fun thought experiment, not a physics test. ;)
Since the OP's post doesn't posit that anything would necessarily change other than us talking to our younger selves, I don't think it's necessary to assume that anything we do to alter our past is automatically doomed to failure. Yes, maybe it stirs up the quantum foam sufficiently to randomize the numbers differently but we don't know that quantum physics works that way since we have no practical experience with time travel. It's a fun thought experiment, not a physics test. ;)
Yeah, I know, just thought I'd mess with the thought experiment :P