On one hand, I can see where they were going with this. The whole sequence from the point that the quartet gets back after the visit to the planet, up to when Reed escapes, is like something out of a Cronenberg film (as HITB mentioned). That whole sense of body horror and these innocent people reacting in agony at their situation would have been quite harrowing if it was part of a different concept or set up better.
However, nothing else works. There is no "family" to it because everyone's completely dysfunctional. It's like they didn't understand the concept of the franchise at all and just wanted to go adult and upmarket for no discernible reason.
Case in point - Doom's one-sided infatuation with Sue. In the comics, every time a male superhero tries to romance or seduce Sue, she only lets it get to a certain point (letting Namor give her a kiss, for instance) just to watch Reed squirm because she does love him. In this, they're both such non-entities that Reed is ignorant of Doom's attraction, and Sue is so high-strung and intellectual that she won't give him the time of day.
The last act is complete garbage, and I'm willing to bet that they reshot a lot of footage to reframe it as a more family-friendly concept.
