Not sure what you are talking about. MGS V has 31 main (51 total) mission across 2 worlds (afghanistan and africa), complete with interesting story and beautiful cutscenes.
Hospital mission is not even longest one, nor most detailed.
I think he's referring to the fact that first chapter had a very coherent story, then in chapter 2, it's just random stuff happening with some occasional story taking place in Mother Base...and then the game just suddenly ends.
Hospital mission is not even longest one, nor most detailed.