Even though you have set "no preferences", you are really saying that you are okay playing with every possible option, and that includes some premium options.
The message is telling you that you will have to wait for a premium member before you can play with any of those premium options.
If you do not want to see that message, just set your preferences as shown in the following image and the warning will go away. But, here is my warning to you: if you do that and a premium member does come along that wants to play with those options, you will not be added to that game and you will have to wait for a different game.
