TwoSix
Everyone's literal second-favorite poster
It depends. The value of a setting is entirely dependent on how shared it is. If only the DM actually knows anything about the setting, then they should change whatever they see fit, and just use the parts of the setting that they deem useful.In my experience, moat players know nothing about any of this, though they may know the words "Forgotten Realms." Settigns are about helping DMs with their prep work: the less familiar the players are with how a Setting "should" be, the better IMO.
But if several players know the setting well, then making broad changes loses the "shared imagination" shortcut that a well-known setting is supposed to facilitate.