It seems people find something to complain about with Spider-Man movies. For every fan of the "power rangers" Goblin from SM1, there seem to be as many who hate it. The Lizard from TASM had a labcoat, but there was an outcry about "snout", though Webb explained he wanted a humanized facial structure that could deliver dialogue, and anyway the design was consistent with Ditko's Lizard. Venom's too small, Venom looked suitably terrifying... TASM2's Harry looks nothing like Goblin should, TASM2's Goblin is a great leap forward from the Power Rangers Goblin, etc etc etc. It goes with the territory to pick things apart in the Spider-Man film universe I guess.
I think had Webb gone with an organic Rhino, big bulky guy with horn coming out of his forehead, it would have been totally slandered by a lot of fans. The way they treated it in TASM2 makes all kinds of sense to me and looks fantastic. How they do him in TASM3 remains to be seen, but I imagine him staying robotic, probably all refined and sleek with red illuminated eyes or something, but not organic.