Earlier quoted context omitted.
It's only a thing if you can define it, but there is no agreed upon definition of what collection of things comprise consciousness. We have all the pieces, and we know we have all the pieces (note: this doesn't mean we don't have a lot more to learn, both can be true). There is little controversy over how it all roughly works together. The only real controversy is semantics: what do we mean when we say "consciousness…
A phenomena can be defined by a pattern, even if it’s not well defined in a technical sense. And a pattern is a thing. Consciousness is an everyday experience that appears to be reliably shared by billions of entities who communicate about it to each other. And have done so for at least millennia. To use a colloquialism: It’s a thing
Replace type with concept and value with thing, and we get a rebuttal using the same language. You can also switch the terms, depending on how 'a thing' is interpreted. If you are more familiar with set theory, replace type with proposition, value with element. The critical difference is between reference and referent.
Further if large numbers of people holding something is true for considerable duration is sufficient for something to 'be a thing', we'd also have an argument for 'the consciousness of the human heart' being a thing, which I don't think anyone would argue in good faith these days. There are probably better examples, but note that the duration of time and frequency of experience are parameters with no obvious values indicating at which point the underlying 'thing' should be accepted as undeniably 'a thing'.
The whole point of requiring it to be technically defined is that all this confusion just goes away and it becomes possible to ask more meaningful and less ambiguous questions about it.
That said, I will concede that the argument I have made does not say that consciousness is definitely not 'a thing', just that it is defensible to say that it is not a thing, given that it is held that either it does not represent a proposition, or that the proposition it represents is not true. (note I'm using the term proposition with some handwaving).