The screenplay of Back to the Future is fun to compare with the original one[1] which lacks a Delorean, but had dull expository scenes, preaching about nuclear war and technical progress, a bit where Marty pirates videotapes and a lot of Coca Cola references.

Perhaps more relevant to the heros journey ideas, a major reason why the original is actually a really bad script is that stuff that happens for a reason in the final screenplay (going to school, attempting to invent rock and roll) is just Marty screwing around and ignoring advice (from the guy he trusts enough to drive into a nuclear test), and he doesn't really get the motivation to get his parents together until quite a bit later.

[1]https://www.mediafire.com/file/rzrz3tynumi/

Seems to fit. Also read about cinematic chiasmus