The meaning behind Terminator: Dark Fate may well on how destiny can’t be changed. Sarah Connor tried to keep her young son John safe and in the future, the elder version reprogrammed a T-800 to prevent his death. When Skynet can mess with the past by sending a bunch of robot assassins to various moments in time, the inevitable has to happen and the question has to be asked, do they go Back to the Future?
A lot of questions are raised in light of the grander picture. Time travel stories are always going to be a head scratcher because of the effects of Schrödinger’s cat in the timeline. Robert Zemeckis’ film (and Legends of Tomorrow) explains that alternate time-lines can be shut down so long the heroes act fast enough before the effects become permanent. That way, only one continuity exists. James Cameron (who’s taking far too long to make sequels to Avatar) returned to his seminal creation to say everything we saw that he wasn’t involved in is all alternate universe material.