I don’t see any problem in principle with physics, say, arriving at an explanation of why the speed of light, or any other physical constant is the way it is. Indeed, that’s precisely what some fundamental physicists are trying to do. Whether they’ll succeed or not is, of course, another matter.
Similarly with consciousness: no reason in principle why biologists shouldn’t be able to arrive at a mechanistic explanation of the phenomenon, which is, after all, a biological phenomenon.
The problem with panpsychism is that it only appears to explain things, but it doesn’t. It simply postulates a new fundamental property of matter, without any empirical evidence to support it. for much more on this, see my 8-letter exchange with a leading panpsychist, Philip Goff: the science and philosophy of panpsychism