"why not tell more in depth stories" because theres a good reason they dont, most people will be getting bored of the story after 3 films its what happened in harry potter alot was just wanting it to end and it just didnt have the same impact of an ending as the books did.
this would be the same with the super hero comics. They have to shorten the stories due most not caring about every little detail and no matter how they did it, it still wouldnt have the same impa...
you dont get the point of this though.
they are clearly going towards a new fresh version on the xmen story and this includes what will happen later on.
The reason why he has brought those 2 back is because they are both amazing actors and played their roles no matter how bad the films were brilliantly and so who else is better to play the old versions of the characters then those who have experience acting them.
In no way will these be playing them in the sam...
this would leave it unbalanced. after 8 films and countless other lore have you not realised "Balance" is true peace in this world there must be dark side and light side. its why even then they thought the Sith was extinct they wasnt.
If anything Luke is most likely closest to balance as if its gone by a lot of the other Lore he will have studied the dark side and realised Jedi and Sith are 2 sides of the same coin they are both the force