The difficulty in defining it certainly makes it hard to talk about. And it makes it impossible to even conceive of how one might detect this phenomenon in other people, or even come up with any sort of theoretical framework around it.
But if "the issue" is that this difficulty means I can't really be sure it's even there, no. As I said, this is literally the only thing I can be 100% sure exists. For everything else, there's room for at least a little doubt. This world, the room I'm in, the computer I'm using, even my own body could all be illusions. But my own consciousness is definitely real.
If you don't feel the same way about your own consciousness, then as I said, you're either taking the piss, you're very confused, or you just don't have it.
As I said, this is literally the only thing I can be 100% sure exists.
Certainly you're aware of things. There are some relevant phenomenological concepts that you hold beliefs about, just like there were real symptoms being described by the Humours system. But you have no justification for bundling them all together into something called "consciousness", which coincidentally comes packed with other, completely unproven assertions.
Seems you agree with me, then. The "you" i.e. me being aware is what I'm certain exists. I'm not sure what other assertions you think are bundled in there, seems like just the one thing to me.