He has to rush Marty to hurry up but he has a time machine. Why doesn’t he just explain the plan and get everyone prepared before TIME TRAVELING to a point where they can successfully fix the issue without being on a time constraint? This is in universe, not in relation to a film itself. I understand why he did it for the movie, but why did the characters Doc Brown do it?
shareThat is indeed one of the rare true plotholes.
They could kick back , get some sleep ,drop Jennifer off, form a plan , gather some equipment or whatever , and then set off to exactly the same point in the future but in two weeks when they're good n ready.
Couple that with the fact they didnt need to go AT ALL!
Doc could just say "Marty, I've been to the future and your kids have grown up to be dicks . Try Harder!"
Ahaaha, that's the best advice from a BTTF pov, good thinking!
But if you've seen the avengers and know that this theory is crap, THUS you know that there's a multiverse, you'd realize that this tip by Doc was going to fix nothing.
Infact, it would just create another universe where Marty knows his kids are dicks but who knows what else changes.
Instead, Doc travels to the same universe and tries to change that one, keeping that same universe with an alternate outcome after 2015.
Maybe Doc likes how he turned up in 2015 and just wanted Marty to fix his kids' act. Or he just loved Jaws 19 and wouldn't want to risk losing that jewel!