Fox kept getting into a loop of making films in order to maintain the rights, which invariable get rushed and subsequently bomb. No one wants to be associated with the pre-existing trash and so, they need to do a reboot and start fresh. The rights became far more valuable than the films over time, as Marvel went from near bankruptcy (who sold rights for basically nothing) to a multibillion dollar brand. Eventually Fantastic Four, along with x-men, basically just became a bargaining chip to extract as much money as possibly when they were eventual bought out by Disney.

Now the rights are in Marvel/Disney’s hands, it shouldn’t need to go through this ever looping cycle of trash every few years.