It needn't be dualism if there is some threshold that makes things conscious, but then people can ask what that threshold is and why, without a good answer people will think you're leaning on dualism again.

I doubt there is such a threshold, I think the issue people have with the idea that rocks might have cognition is it too difficult to perceive the difference in scale of complexity of a brain compared to a rock. People have trouble comprehending the idea of a millionth, going further than that there is the intrinsic difficulty of accepting something existing at a scale you cannot perceive or even conceive of what that might be.