First off, there is no accepted definition or test for consciousness. The concept is something we cannot prove even exists (outside of magical or imprecise, human-centric definitions).

Second, there is no common definition of thinking that requires consciousness as a prerequisite (that seems to be a false/invalid statement you're making to try to gloss over accepted definitions for thinking/intelligence that describe/fit AI agents well).

And third, if we can't prove consciousness even in animal species close to humans (or even other humans) in cognitive abilities, then you cannot in good faith (being honest about what we know or don't know empirically) say that an LLM Is not conscious (and the same goes for an LLM thinking or having intelligence).

It is more likely that humans made up a term (consciousness) to try to separate human intellect from that of other animals (for veiled religious and mystical reasons, along with concepts like "the soul") and now people are falling back into that flawed definition in new quasi-religious debates around AI (like the debate around evolution previously) that challenge our deeply held (but flawed) beliefs/opinions around our understanding of our own abilities and our incessant need to feel special/supreme in the universe so we don't have to come to terms with hard realities and nuanced understandings about the reality in which we live.