This came to me in an epiphany the other day. I'm sure this is not original wisdom, but I'm not sure who I'm borrowing from so I'll gobble up all the credit for myself.
The past is not part of a "timeline". Forget about "timelines". The past is an instruction manual to the present and future. Conceiving of the past as on the same line with the future means you are lumping what you can change in with what you cannot, like whiling away your time before an exam by wishing for a bigger brain instead of studying.
If you wish for a time machine to go back and change the past, you are wishing for the facts in your instruction manual to be deleted and replaced by fantasies. This is a natural tendency. It is childish rather than evil. Maturity means focussing on learning and responsibility. Responsibility is the reality of freedom; superpowers are the fantasy.
This is a discipline I in particular need since I am an incorrigible dreamer. My fondest dream is the First World War never happened. The dream is beautiful but ultimately it is a burden.