I would suggest you not eliminate the main dining room. Casual and Smart casual are basically kaki slacks and a button down shirt.
The food in the Windjammer (buffet) could be good or could be disappointing.
The food in the main dining room has many options including their standard salmon, beef, and vegetable meal. You can also order many different meals each night (which I have done many times). I always order a meal and the Indian dish because I like spicy food.