I think it's pretty telling that the example I was going to bring up of the only decent looking 3D comic I'm familiar with being The Dreamland Chronicles...
....years later since when I used to read it has been remade as a non-3D comic with more traditional illustration.
It used to look like this:
Which at the time was pretty good! ....But now it looks worse than the realtime graphics in a videogame, which is pretty sad considering how much work it used to take the creators to make all these custom models, light all the scenes and render out all the shaders.
I do think it's possible to make a good looking 3D webcomic, but honestly the only likely scenario in which I'd ever consider it is if I lost my right hand and couldn't draw any more, but was still able to use my background as a games artist and knowledge of 3d modelling, texturing, lighting and shaders. Unfortunately the way to get the nicest results most easily, drop everything into Unreal Engine (It has fantastic default lighting and PBR shaders), would probably run into licensing issues down the line, so I'd probably use something like Blender or Unity, set up scenes, light them etc. Overall though, the problem with 3D is while it's probably doing to get a better looking result than drawing for a person who can't draw at all, to match the quality of somebody who can draw decently or well the amount of work you need to put in and the level of expertise required to make the assets just explodes, and you have to ask yourself "wouldn't it be better to use these assets for animation or games?"
