I never saw anybody saying it literally "looks like" D3. Obviously it has a darker color palette, obviously it has a more "foggy" and dark'ish style. Anyways, the gameplay and game mechanics look like a blund rip-off of Diablo 3.
That is what people mean by saying that.
It will be (and it HAS to be) the same arcade console gamestyle, because it is getting developed for consoles and joystick players. Anybody who fails to recognize that is the one who is brain dead. Diablo 2 and its game mechanics never fit in into xbox or ps4. Anything is dependend on that... The joke of a "skill system" (which doesn't let you any freedom or real choices), the joke of the stats system (which doesn't exist anymore) and the itemisation ("weapons demand your skill damage output").
If they don't want to fuck up the game experience on consoles, they have to do the same bullshit they already did in Diablo 3, simple as that. The only good news is... Last time, they could have created a Tetris-Clone, Diablo 3 would have the same selling numbers, just because of the name "Diablo" and the greatest arpg ever created (diablo 2). This time... nobody will blindly fall into that again.
My prediction is: D4 selling numbers will be magnitudes below D3.