> When rapid progress is made in a poorly-understood field, then how can our definitions and requirements for success not change?

It's in how they change, not the fact that they change. The skeptics seem to have secret definitions for intelligence, sentience, consciousness, creativity, etc. that amounts to "a thing only humans have". Often that thing is equivalent to a soul. When yesterday's challenge (LLMs don't have X because they can't do Y!) is met, Y changes but X stays the same. This is not the process by which a field matures, it is a rhetorical technique used by skeptics to avoid honestly stating or confronting their internal definitions. That can be revealed by asking the skeptic the following:

"Forget LLMs. What if we made a completely physically accurate simulation of a human being?"

Many say no, that simulated human being still couldn't have (intelligence, consciousness, sentience, creativity, ...). This reveals that there is a necessary metaphysical component to those attributes, at which point any scientific-minded person will leave the debate.