Readers will buy anything, if you can sell it. Vampires, wizards, talking animals, superpowers, sentient flat figures... Readers don't look for a realistic story. They look for a good story. Any premise will be accepted, if that's what is needed to tell your story, and if your story is good.
Take House as an example: the premise requires a doctor so caustic, that in real life he would never have been allowed to keep his practice. Also, most of what they actually do is plain wrong. Does anybody care? No, because the story is good. (Or at least, good enough.)
One thing you do need to keep in mind is consistency. If your setting is not internally consistent, that's like a hole in your sales pitch - everything starts to fray around it. Whatever your setting is, you're asking the readers to suspend their disbelief, and accept your setting as is. Which the reader is ready to do. But the moment you start to contradict yourself, you punch a hole in that suspension of disbelief - the reader cannot simultaneously accept two contradicting prepositions.
So long as your story is internally consistent, any setting whatsoever is fine.
If you're still uncomfortable about a particular element, you can try to justify it within your story, but that is risky: you would be drawing attention to where the fabric of the story is weakest. Sometimes it's best to ignore the hole, accept it as part of what's necessary to make your story work. Like the House example.