How so? It was hardly just a tech demo as the gameplay elements all seamed fairly obvious whether it was the scavenging for items to combine into tools and additions to weapons, to the frantic gameplay where running away and using the environment in conjunction with your weapons to slow and stymie the horde as you thin them out was very obvious, the variety of ways to use the open world in conjunction with this. So on and so forth. There was nothing obtuse or vague about it, especially when we got the alternate play through that further high lighted these elements.
Scavenging and "crafting" looked barely functional in terms of UI and use. Actual gameplay boiled down to nothing but attracting a horde to run away from and use poor environmental obstacles to slow down.
Feels exactly like watching the early Splinter Cell Conviction hobo Sam gameplay. Nothing felt frantic as you say, just a proof of concept for the horde numbers and barely functional/recently implemented scavenging and environmental interaction. If this game isn't in development trouble I'd be fucking shocked.