[Nicolai P. Zwar]

It all depends on the situation. I agree that some franchises use flashbacks (and prequels, and whatnot) to explain and show backstories that should only be hinted at.
On the other hand, as I said, flashbacks can be masterfully integrated into the story, they can be revealing (like ONCE UPON A TIME IN THE WEST), or the flash forward and backward can heighten the story (like Leone’s original 4 hour cut of ONCE UPON A TIME IN AMERICA with lots of flashbacks is much better cut than the truncated US chronological cut), or they can BE the story (like AMADEUS or CITIZEN KANE), or they can even be essential to the story (like RASHOMON). So flashbacks are like any other device, if they are done well, great, if not, not. No movie is better or worse simply for using or not using flashbacks.