I have no idea why did Kojima decide to split the game in two, but GZ seems kinda lame. It lacks interesting content (however, the deja vu and jame vu missions are a joyful addition for old fans), the gameplay is literally a cut version of the one from TPP, and the whole plot is a seed for the TPP, which could've been included in MGSV, but no, let's sell a demo for 20 dollars, okay.

I honestly don't understand this Kojima's move. Literally the Man Who Sold the Demo.