I have the Avalon Hill boxed set of RuneQuest, which was my first exposure to the system and the setting of Glorantha. Back then I was coming from a standard fantasy mindset, that fantasy was elves and dwarves etc. I will say coming from that mindset, I was a bit... not exactly put-off, but more puzzled, when I found out about humanoid ducks. It just didn't fit into my view of a serious fantasy. Like a fantasy version of Howard the Duck. These days it doesn't bother me, but I can see why some players may be put-off by such things. So I think it's true that separating the system from the setting in this instance may bring in more players that normally would be put-off by the setting.