Though I don't have the sentiment as strong as Gilahu, I think I understand it. It's not a matter of pieces existing, as it is how they look. The CCBS system has a very smooth, refined look that is different from the piston/gear look of G1. Of course, there are exceptions, in particular the new piece G2 introduced.
If you look at Surel, even though the helmet and blade aren't real pieces, they look like parts that would fit in with the style of G1 parts. And you can easily see identifiable bionicle pieces on the rest of him. With Nikila, it's harder because the drawing is very stylized, but it still has a resemblance to ye olde bionicle parts.
Now, however, I shall counter Gilahu's argument with this: as was brought up in another topic recently, bionicle sets (and by extension, canon mocs) are a representation of the character, not an exact 1:1 image of what they look like. Different art styles have reflected the characters differently -- take for example The Legend Reborn vs the Miramax trilogy. is it such an issue if different build styles --G1/CCBS -- depict a character somewhat differently?