Unrealism doesn't necessarily mean just form of the character in the image, it can also mean what's shown in the image - is something unrealistic happening? Nevertheless, I don't doubt that realism is a significant aspect for some people, but those aren't the same people as the lolicon community, and the people who really do believe in the "2D > 3D" meme. I'd also wager that a good portion of recent stuff tagged with 3d isn't loli or shota, and could be in part explained by the popularity of SFM/Blender porn of 3D games like Overwatch.
In any case, it stands to reason that people who would enjoy real child pornography would also enjoy simulated porn (and likely, the more realistic (3D) the better), but it doesn't therefore follow that the majority of people who enjoy the less realistic content (which by far outstrips the 3D content) have the same tastes.
In any case, it stands to reason that people who would enjoy real child pornography would also enjoy simulated porn (and likely, the more realistic (3D) the better), but it doesn't therefore follow that the majority of people who enjoy the less realistic content (which by far outstrips the 3D content) have the same tastes.