USUALLY it is, but there could be reasons it is not. I have zero issues going to the MDR on the last morning, so I've never bothered to go to the buffet so no clue how busy it is.
I've never minded the MDR on the final morning - it's nice to be served and have a chance to say a final good-bye to my service team. (Funny how the "it's so nice to sit and be served" argument so many use for the MDR first day lunch goes out the window on the last morning...)