Heroes are supposed to have higher standards then the villains, when that doesn't happen the heroes just look like moralising and hypocritical assholes. It doesn't matter that Doom imprisoned the Fantastic Four and tortured them, such behaviour from the monarch of Latveria towards uninvited guests is to be expected. If anything the Fantastic Four should be flattered that Doom prepared such bespoke forms of imprisonment for them. If the Fantastic Four are in any way surprised and upset by the situation 70 years into this relationship then they are in the wrong line of work and completely out of touch.
I get where you're coming from but I can't help but feel that Franklin feels like a spare wheel at the moment. Too young to go on the more dangerous missions but not old enough to be independent in his own right. At least if Franklin was a mutant he could find a place on one of the X-Men's junior rosters in a team book with an ensemble cast. As it stands Franklin is just going to be overshadowed by his more famous parents.