Why people adore Back to the Future and dont fall for this kind of movies.....
Big problem - they estimated at he beginning that "Trying to change the past is bad and will not work" with Bruce speech and basically told the audience that its pointless and there is no way Barry will save mommy and there will be happy ever after. And then with that spoiler ahead people had to sit for 2 hours and watch him fail.
Happens so many times in time travel movies and its annoying.
This is why people adore Back to the Future movies and keep rewatching it. Because in there Marty actually succeeded. He went back, screw timeline and changed what he wanted to better and there was happy ever after.
They really should stop doing this trend and let characters change things in the past and not fail.