The clean 3D render look comes from product visualisation, where the job is to show an object clearly before it exists. Nothing in that context is allowed to be atmospheric: the lighting is a controlled rig, the background is seamless, and every surface is a material with a stated roughness rather than something weathered by use.
The soft, toy-like variant everyone recognises adds two more decisions. Materials are matte clay with almost no reflection, so form is read purely from shading. And global illumination fills the shadows with bounced light, which removes hard edges entirely and leaves only gentle contact shadows where objects touch.
Isometric framing is the third convention, borrowed from technical drawing. Without perspective convergence, a scene reads as a diagram you can inspect rather than a place you are standing in β which is exactly why it suits interfaces, icons and cutaways. Say isometric to Artlist and the whole composition changes.