Emergent property of a sophisticated brain (with it's own weaknesses).
But even if I didn't have a more compelling explanation, that doesn't mean I can't be highly critical of, or reach a conclusion that panpsychicism is highly unlikely to be approaching a good explanation.
But also, see the rest of my comment. The onus is not on me to arrive with a better explanation just because there's a bad explanation on the table.
If I come home and find a cookie on my counter, and someone said "I think that a space alien teleported the cookie there" and I said "I think that's unlikely to be the correct explanation." And then that person asked "Well, what's a better explanation?" and I said "Maybe someone broke into my apartment, felt guilty, and left a cookie there." and then grilled me on that counter-explanation.
I genuinely think emergent property of sophisticated brain is much closer to the correct explanation than panpsychism in terms of usefulness, predictive power, etc., and likelihood of getting closer to a satisfying answer. On the other hand, I'm not prepared to defend every aspect of that hypothesis. I am, however, prepared to criticize panpsychism.
But even if I didn't have a more compelling explanation, that doesn't mean I can't be highly critical of, or reach a conclusion that panpsychicism is highly unlikely to be approaching a good explanation.