As an example, the Red Wizards of Thay (an FR magical organization/magocracy) underwent a transformation between 2nd Ed. and 3E. They became a "kinder, gentler" trading nation forming magical mercantile enclaves in lands that would let them in. The thing is, 2nd Ed./3E Red Wizards probably look pretty weird to Cormyreans and Dalesmen. They shave their heads (including the women), speak a different language, and have a lot of magical tattoos. They're also darker-skinned. After a few centuries of being regarded as pariahs everywhere west of the River Sur, they show up in these places and are doing business -- questionable business -- in broad daylight.
The not interesting thing to do (IMO) with that shift as a scenario or story designer would be to have a pack of bad guy Thayans in an enclave with the good guy locals saying, "Those darn Thayans are up to something, please help us, heroes." I was intrigued by the idea that a Thayan enclave could contain a "new guard" of diplomatic Red Wizards and an "old guard" of fireball-hurling hardasses who aren't allowed (or are discouraged from going) outside. Some of the new guard genuinely want to mend fences. Others simply want to use it as a way to re-establish safe power centers and observation posts in lands where they previously would have been killed on sight.
The new guard use concealing/lightening makeup, don wigs, and wear "western" clothing to fit in. The old guard chafes at having to conceal their heritage and suffers under the jeers and slurs of locals if they dare to appear in public. The new guard speaks with good and proper "Common" grammar and pronunciation, not stumbling over foreign sounds and linguistic concepts. I thought it would create a more interesting and nuanced relationship between the Thayans, the Dalesman, and those who interacted with them, lending sympathy to the traditionally "villainous" and creating a more agonizing struggle between the sub-factions of the Thayans.
An old evil wizard who strokes his beard and cackles as he unleashes chain lightning on random townsfolk isn't particularly sympathetic. But suppose he were a veteran Red Wizard who watched his fellows succumb over the years in service to the zulkirs and was forced to "step aside" as young diplomats smooth talked their way into trade relationships with their former enemies. He has to endure the insults of locals, hear them mock his clothing, his pronunciation, his skin, his culture. And when he expresses his frustration to his new (younger) "superiors", he's treated like an anachronism, an old artillery cannon left to rust and rot on a forgotten battlefield. That dude may still wind up casting chain lightning on townsfolk, but if we weave a compelling story around him, the player should feel that there's more to him than that.
.....
"Okay, so let's suppose all of this stuff about the Realms is true. What does that really mean for how the people in it live their lives?" It made the world more dark and grim, and sometimes that consideration wound up bucking convention, but we didn't set out to invert fantasy conventions just for the sake of doing it.