As long as it's "isometric" and pretty I don't care if 3D or 2D. As evidenced in this thread, often people can't even tell the difference.
FYI, this is "hand-painted":
Infinity engine is not. Neither is Statis, or Inquisitor.
The only issue with 3D is camera, front objects obscuring the view etc. but this can be taken care of if optimized with that perspective in mind which most modern games sadly don't do.
IE games, Stasis, Inquisitor have pre-rendered backgrounds. They were made in 3D, but what is in the game is a 2D picture, the result of the render. What you are talking about is a distinction in how the 2D image is made - by pixelart, or in a 3D program - but the image in the game is still 2D.
That is still a difference with a 3D background that is composed of 3d elements that are rendered in-game, such as in the NWN games. The world is not a picture anymore, but is rendered in-game out of 3D elements.
That is the distinction that people talk about when they want a "2D background", and not how the 2D picture is created.
People that are unaware call the IE games "hand-painted", which just shows how pretty they are, but nobody cares how the 2D image is made, just that in the game it will be a 2D image, and not 3D, textured objects.
On topic: if anyone really needs convincing that the IE games look better than 3D rpg's, then this game is probably not for them.