That’s bit harsh to say that all his great works are not his.
I do share the sentiment that Kojima’s writing has been in downhill for quite sometime and he really in need of a good editor. I actually think that his stories are more coherent or at least entertaining in his earlier works, e.g.
Snatcher
Policenauts
MGS 1
Some like MGS 2, but I think the boring oil rig setting broke me, and the constant chatter with ‘Colonel’ didn’t help
MGS 3
Peacewalker
MGS Rising
What I actually like is his obsessive attention to details that barely matters when it comes to gameplay, e.g. melting ice cubes, aiming at enemy’s crotch to get dog tags, etc.
Kojima games started clicking for me when he introduced the ‘R&D system’ in Peacewalker, where it’s actually a RPG progression system but the rewards are absurd equipments. As the matter of fact, I like the ‘walking and R&D’ parts of Death Stranding a lot, but really dislike the enemy encounters and the story in that game.
And it’s okay, not every games are for everyone, I’m glad that someone is giving him blank cheques for his absurd ideas that are not the norms.