Yeah, the fact that he couldn't communicate with others apart from shouting out the occasional "NO!" or "Arcane!", and that his only power was the same-old generic "ability to beat people up" thing, didn't make for the most interesting character once you got past the pathos of him being a "muck-encrusted mockery of a man." Moore's retcon, not only of Swamp Thing's origin but of his powers and very nature, is perhaps the most ingenious in comics history.