If someone doesn't know what "critical" means, they also don't know what a "correlation length" is, so I don't think this clarification is very helpful. Who was the intended audience?
We don't just learn a new subject through simpler ELI5 explanations.
We also learn by immersing ourselves further into the subject (like here, were we were given an alternative, still elaborate explanation), until things "click".
In immersive learning (like how kids learn language and most other wordly things naturally outside of explicit teaching) we also get to understand the meaning of an unknown term by compounding other unknown terms, and making correlations, connections, and deductions.
Presumably the “correlation length” is something kind of like “some length where there is much larger correlation of pairs of things at most this length apart, than there is between pairs of things that are much longer than this length” (but that’s largely just a guess)
> Who was the intended audience?
From that definition? Obviously physicists, lol