Owen doesn't go back in time because Nux is still ALIVE, thus making it unclear of what the consequences/repercussions are this time around, because all of the previous attempts of Owen going back in time was only done after the CURRENT timeline Nux is DEAD. So Owen is left with no choices, because repeated actions of rewinding time had cause energy overload/time paradox, which in turn cause a few possible scenarios:
1. Nux existence being erased completely from certain time period, example: like when Owen visited Nux too frequently when he is on Earth at 16 years old, Nux existence at this particular time period straight up disappeared and no one remembers him, like a disconnected in reality
2. The events of the past change completely, meaning that events that should not happen at particularly time period started happening and some event that already happened in the past don't happen
Considering all this possibilities that going back in time will only cause Nux existence more damage because of energy overload, Main Owen/Asperier doesn't have any choices except to stay in current timeline, making him at last go a little crazy/depressed from being unable to redo things because he himself is unsure of what the consequence is if he try to go back in time when the current Nux is still alive.
So to get things straight Owen was after Nux from the start because they has met in an alternate timeline he fell in love and all was well but Nux dies, he turns back time tried to change the future but Nux still dies. And Owen goes back over and over again ducking up the timeline and keeping the bodies of the dead Nux's and make a statue of him when a body disintegrated. Now because this timeline he had Noi something else happens and there was an issue with a timeline. All we know is that he left Nux without going back in this timeline for a reason none of them are explaining.
My biggest question is, is he the reason the rewind didn't happen was it the existence of Noi that doesn't seem to be in any of the previous timelines ..or even foreshadowed. Why didn't he go back this time... And how does the baby tie into this shitshow????