Kojima has definitely been this kryptic before. Death Stranding is nothing new. He was just like this between MGS2 and 3. As for gameplay, what you saw was "real", even if you didn't like it.
I trust who's in charge. He's yet to let me down.
The thing you are not understanding now, is that those cryptic teaser/videos he released before; and all that weird, but good marketing; was about a well established franchise, in which people already knew the core mechanics of the game. So right now Kojima is being crptic as fu(K; BUT on a new IP, so people dont know what the game is, nor how it played since there have not been any other game in that franchise.
That is why people cant take into a context much greater what they saw on the video, for most people the whole context is the video; in which the character just walked. Kojima should have explained after the video ended that he just showed the "stealth" in the game since you can fight those creatures too. But I guess the weird Sony format of the conferece did not allow it.