Only if suddenly ALL games had to be create a character, but in general opening up the available playable characters to other genders or minorities doesn't really limit developers creativity... it just makes them work harder.
I mean ESPECIALLY in games like CoD, AC and other annual or long running franchises, where the main character is basically a blank slate or a archetype that is repeated in different settings. Creative folk like to do different things, being given options or told to make some of them work either makes for a richer experience or shows your story was weak to begin with.