Watch the videos for it in the store page, it's clearly showing the game's goal is to throw zombies at you while you struggle to put a base up for the horde night/gather supplies for the night. A16/15 was nothing about tower defense, or defending against zombies. You could walk right past them and say "Hey zoms how you all doin? No, we're not going to fight today, I want to roleplay a flower picker if that's alright with you all". You can't have tower defense and surviving a zombie horde with no action, no digging, no zombies doing damage to walls, it's not going to work out and can't have both. Nothing in advertisements for the game state a survival aspect like... idk The Long Dark or whatever it's called. The primary goal of the game was never "find food and water and stay out the cold and you're doing the game" -- I doubt the game was ever hailed as a "Survivor Man" show-game. Its surviving zombies that want to kill you, while not starving to death or getting a deadly infection.
The game didn't feel like tower defense because they didn't have the proper AI and whatnot, now that they do it's here.
If you don't eat and drink in the game, you die. If you don't craft anything, you die by zombies. How aren't they primary aspects again? I think people forget this is surviving the zombies game, mainly because zombies were a mere 'flair' that you could choose to deal with or choose to not deal with.