I'm getting a headache looking at these forums when 90% of the things can be answered oh so simply.
ALPHA STAGE
ALPHA STAGE
PLACE HOLDER SOUNDS AND TEXTURES
From Alpha to Beta and Beta to RC you'll see a difference in textures and graphical features. Until then, good lord.
Except you don't release a gameplay trailer full of placeholders, now do you?
4 years into development, and 8 months from release, is not in alpha.