Once upon a time, a group of women went shopping for ice cream.
The first bought super-fifteen berry banzai suprise.
The second bought extra-dark bitter mocha chocolate with almonds and hazelnuts
The third bought super funky cookie dough monkey delight.
The fourth bought plain old vanilla.
They took their purchases home and tried them out in a variety of ways.
The first woman's ice cream made a great milkshake, was okay with pie, but made a terrible banana split.
The second woman's ice cream was great to eat by itself, but made a terrible shake, was disgusting with pie, but was not bad with a banana split.
The third woman's ice cream was decent in a shake, not bad with pie, but horrible for a banana split.
The fourth woman's ice cream went well with everything.
Ever tried to create some 'concept campaign' with a group of players, only they all show up with a variety of character concepts they want to play but don't fit your mold?
Or alternately, as a player, have you ever had a great idea for a character, but it just didn't work with the campaign the DM had devised?
There's something to be said for plain vanilla fantasy worlds. They leave room for lots of different character types and backgrounds, as well as multiple play styles.
Vanilla doesn't mean flavorless. Ever tried some home made ice cream WITHOUT any flavoring? Makes vanilla taste amazing after that. It's just a flavor that's well known and comfortable for a lot of people.
For a DM, that means less work you have to spend on exposition. For players, it's less work trying to figure out how to fit into your DM's world. That means you have more time to play, and that's where the real fun is, isn't it?
There's nothing wrong with a 'plain vanilla,' pseudo-western Europe with pseudo-whatevers on the fringes, because that means more time to play and less work/homework for everyone.