Sorry you have this completely backward. Let's have a history lesson. The first FF film was a modest hit, at least good enough to warrant a sequel despite the fact the film was panned by critics and met with tepid response from the fan base. The sequel was "better" but still a disaster but worst of all, it did worse than the first film. The franchise was shelved until the 2015 reboot.
The reboot was a case where Fox was interested in dipping their feet in the water, but it was clear they wanted to do the film on the cheap, with an untried director, and a cast of up and comers they could pay cheaply. When word got out about the film being a disaster needing multiple reshoots and forcing Trank out of the editing room everyone knew this film was a complete screw up.
The executives you're talking about are not going to spend a dime on any future effort, because on a third effort the film was the biggest bomb of the bunch. Even ROTSS wasn't a bomb, it was a disappointment for sure, but it wasn't a bomb.
So you tell me what exec is going to put his job on the line by committing money for the production of something that after three efforts, each one made less than the previous.
Fox can either just decide to be d**** and make a required movie every so often in the hopes they'll get a cash out from Marvel, or try to negotiate the rights back for something else they want, or just let the rights revert.