When someone like Erik Mona casually uses phrases like "typical of Planescape's slap-dash approach to fiends" he forgets how painfully thin the amount of total fiendish material was before Planescape and how detailed, complex, and painstakingly thought-out (and genuinely scary!) the fiendish ecologies in Planescape really were, especially as Colin McComb presented them. I consider that to be both style and substance.
Well, in all due respect, it was kind of slap-dash.
Faces of Evil paints the fiends as pretty horrific creatures, unfortunately it also paints them as more... humanoid than I (and apparently others) would like. At least with me, it's not the fact that Shemeska and A'Kin are merchants, it's the fact that fiends are encountered
at all in Sigil. The opening scene of
Fires of Dis has a freakin' Glabrezu bartering with a merchant. The fiends have lungs, they breath, they have organs similar to those of other humanoids (at least, the baatezu do). It's all too humanoid for me.
It doesn't help when the
Planescape Monstrous Compendium I is full of many decidedly unfiendish illustrations (I never cared for Rex or Post's illustrations). For pete-sake, the Arcanaloth has
glasses on!
While, many perceptions of PS may not be true of every fiend in the setting, these perceptions ARE reinforced by certain characters, some of the flavor text, and a lot of the art.
I fully believe that PS would've been better received if it wasn't locked into the Core Cosmology and was instead an alternate Cosmology. I know that when I was reading through the old 1e Monster Books, I wasn't expecting the fiends to speak some slang cockney, wear funny hats, or look all cute, not to mention run stores.