The only ways MGSV should have been more like Horizon is by having a good storyline that finishes properly, and ditching the explorable (!) Motherbase.
I think people misconstrued what Kojima intended when he created MGSV as an open world game. As others have said, he just wanted bases that could be infiltrated from many angles using many different means. He wanted people to be able to travel towards them from far away and plan their approach. He never intended for there to be sidequests and RPG elements filling that world. I think it was a mistake having us collect plants and animals everywhere though as this did seem to communicate the opposite.
I also agree that graphically Fox Engine is right up there with Decima, if we take into account its target framerate, year of production and the platforms it released on.
I do see the similarities between the two games in terms of controls though, and while there are obvious differences they both seem to pleasingly put the controls at the top of their priorities.
