On the contrary - I am making a single point, namely, that one of the greatest and most revered fantasy worlds of all time enjoys that status although it has not realistic economy, no realistic politics or history (look at the absurdly enormous timelines in Appendix B), etc.
This is because consistency of that sort is largely irrelevant to most fantasy advenrtures. It is a quirk of a certain approach to RPGing, which has its origins in wargaming and accountancy-style boardgaming, that the opposite view is often exrpessed.
In my view, the details of what plane Eladrin come from, or what layer of the Abyss Demogorgon lives on, is in the same sort of category. These minutiae are secondary to running a fantasy game with a vibrant and engaging imaginary world.