The "Jackie" scenes killed this movie, no pun intended.
Kennedy was alive in Dallas for about an hour, and his casket flown out of Dallas just a couple hours after that. Nearly every cop, secret service agent, witness in the plaza and people in the hospital have been identified and interviewed. This could have made for a very interesting witness testimony-based film along the lines of Downfall (2004). They practically could have done it in real-time. I suppose that's what I expected with Parkland.
I was really turned off by the drama and overacting in the trauma room sections – Mrs. Kennedy wailing, everyone calling her "Jackie", the teenage doctor trying be taken seriously as an actor, etc. I laughed when I saw them place the pink pillbox hat on Kennedy's chest as they roll the stretcher down the hall.
The other scenes & actors were nowhere near as bad, and I knew nothing about Oswald's family, but after a little too much Jackie drama I didn't even make it to the end.