[Question] Gen 4's Unique Visual Style

So I'm trying to make a fan game in Unity, but I'm very confused. I'm trying to copy the graphical style of Diamond, Pearl, and Platinum but it's very strange. Can any Gen 4 experts help me pls?

What I'd like to know is what is in 3D in Gen 4 and what is 2D in Gen 4 and whether a perspective camera or orthographic (isometric) camera is used to view the world. Also, any advice in general of how to emulate the visual style of Gen 4 in my own game would be very appreciated.

Thanks.

Why not just make your own unique style?

I believe most of your questions can be answered by playing around with Pokémon Unity to understand how they mimic the 4th gen style games.