I disagree. While I certainly love my Bee Bullets, ghosts, and nanomachines = super powers, at this point, I've kinda had enough. Part of the reason that I loved MGS3 so much, even compared to the other Metal Gear games, was that for all its cucko, it was pretty serious and grounded and hinted at a Metal Gear that was still fantastical but also still closer to actual espionage and special forces missions. Metal Gear has always been its least fun (for me) during the actiony, ran-n-gun sequences, and the boss fights have always been hit or miss depending on the set up. For example, the fights against young Ocelot and the End were super fun for me, but the (multiple) fights against Vamp or the various B&B fights were just tedious.
So maybe I'm the crazy one for hoping that Metal Gear could lay off on the hard drugs and present a story and gameplay that were more focused, but from the trailers for the Phantom Pain I'm sure we'll be getting plenty of "is this really happening?" insanity. I guess it's probably better than way, for without that zany bits the actual "story" of the Metal Gear games would be pretty bad, for the most part.
Serious or insane, as long as the gameplay continues to be fun, I'll keep loving my MGS!