Hating the Iron Duke seems to me just the same as hating the Malaise Years in general. GM screwed the pooch by making an aluminum L4 and putting an iron head on it. I mean, yeah, there were many other sins invested in the Vega program but that one epitomizes the project. The Vega's entire engineering ethic was akin to the scene in "Dumb and Dumber" wherein, somewhere in Kansas, the fuzzy van gets traded straight across for a moped.
The Duke was the next logical step. But instead of utter failure on all fronts, what was produced was...
A generally reliable lump which (like everything else of that era) made disappointing power at a low redline.
In the context of the Carter years, that was progress.
Now as to the Fiero? The story is well-trod, and we all know it by now. The car was a hodgepodge of compromises hemmed by budget considerations. And damned if it didn't almost work. By the time it was canceled almost every stupid mistake had been remedied. Alas, that is the story of GM during the time of Rivethead.