The director slammed the studio, blaming them for ruining the movie.

Here's a little conspiracy theory to chew on:

What if Fox wanted the F4 to fail, so when they wanted to get the TV rights for the X-Men, they had something to exchange w/ Marvel? Let's say Fox originally set out for this movie to do well, but over time realized that juggling two different franchises wasn't worth it for the studio. And seeing WB/DC do so well on TV, why not take the incredibly popular X-Men franchise & put them on TV? Well, w/ Marvel maintaining the TV rights, that wasn't going to happen. But...

"how about we give them the F4 back for the X-Men rights?"

"But, Mr. Murdock, we're currently making a F4 movie!"

"Bloody well make it fail then, mate! Give those wankers back to Marvel so we can utilize our more popular franchise! They'll do anything to get the F4 back!"