You are absolutely right saying that rule of law is not sufficient condition for the existence of modern society. It was a bit confusing still, because nobody claimed the opposite: the comment you replied to was saying rule of law is a necessity.
You may have been saying this but the parent comment that spurred the discussion was making the explicit assertion that "the rule of law is the only thing holding together [...] everyone's countries, and civilized society in general".
Saying that law is 'the only thing' necessary for the existence of modern society effectively means it is also a sufficient condition. So yes, someone did claim the opposite.
I doubt that modern society does fulfill the sufficiency criteria [1], so „the only thing“ can be right, but also it is not the claim that it is enough for survival.
[1] USA regressing to a globally disrespected oligarchy under Trump is a good example.
Not in my wildest dreams I imagined Brazil would give the good example for prosecuting a former president who attempted a coup and that the US would fail to do the same.
