How do you know even Kojima doesn't like to talk about it? He didn't write or direct it, but he was still a producer and Kojima Productions still developed it.
It was a fun game at the time. The story wasn't as deep as the rest in the series, but you see a young Campbell and a young Gray Fox.
Kojima doesn't give a **bleep** about that game, it is canon, but he doesn't consider it a main line game. The game isn't even in the Legacy Collection which includes everything, even the digital graphic novels and VR Missions.
I think the one line in Peace Walker that mentions the events of PO says it pretty clear.
Finally, we can leave all that crap in San Hieronymo behind...