I think Tom DeFalco can be a very good writer, but not even good writers are perfect for every type of superhero.  I was not impressed by his run on FF and had dropped the title before Alicia was revealed to be a Skrull.  As I "followed" the title by quick glances on the stands later, I was happy I was no longer reading the title.  Even if I had not appreciated the maturing of Johnny Storm through his relationship with Alica during Byrne's tenure, I don't think I'd have liked what DeFalco did.

As for Englehart's run, my take is that he did bizarre things simply to do bizarre things.  His "New FF" suffered from having the team be too similar.  Crystal offered some variety, but 1/4 of her powers were essentially the same as the Human Torch.  And Sharon Ventura's Ms Marvel offered nothing different from Ben Grimm.  Turning her into a She-Thing (which made her character not only a clone of the Thing, but a clone of She-Hulk as well) was not one of the brighter ideas to come.  It also did not help matters that Englehart dropped Reed and Sue so they could have personal time, and then they ended up fighting in the Avengers!

I enjoyed Simonson's run immensely and was saddened to see him leave the title.