Naturalism, often called "materialism," posits that nature is all there is. Panpsychism doesn't dispute that. But the panpsychist also thinks that consciousness is real — present in all nature (or all living nature) but especially developed in humans. Last Monday, writing about a classical atheist naturalist who was attacking panpsychism, I reflected on the difficulties the trend to panpsychism presents him.
The naturalist is hostile to the panpsychist because he assumes that human consciousness will, in due course, be explained away. It is either an illusion, or an aid to survival that evolved among early humans. Or perhaps it is a spandrel (in evolution theory, a useless accompaniment of useful traits).
In short, what we thought was our means of understanding the world is just another part of that world. It's not a place we can stand that gives us some insight.
Comment: Human beings have always instinctively understood the pervasive nature of consciousness in the world. From the attributions of qualities to a particular mountain or lake, to warriors naming their weapons, to the names given to ships or personal vehicles. The acknowledgment of that consciousness can be seen in the 'whisperers' of animal species, or even mechanics who 'have 'the knack' for machinery, which of course are a product of consciousness. The naturalists would have us live in a dreary world indeed.