I think “At such an assembly as this” is descriptive of the tone of the assembly, Darcy says “a collection of people in whom there was little beauty and no fashion” (4). I think “fashion” is a word Darcy uses to distinguish the appearance and behavior of people belonging to his social sphere. This is my interpretation and of course you or anyone can interpret it differently.

I agree Darcy sees the people at the assembly as a bunch of strangers but to me it is not descriptive of the tone of the assembly.

No, Darcy never says the men who have neglected Lizzy are inferior but since I believe he thinks all the locals at the assembly are inferior then the neglecting men are as well. I did say on what text I based this interpretation previously. Do you think anyone at the assembly was equal in consequence to Darcy?

Do you equate Bingley’s consequence with the folks at the assembly?
Are you suggesting Darcy did know Lizzy particularly and was ready to dance with her at Lucas Lodge in Ch. 6?
You are saying Darcy is blind to Lizzy’s good parts because she is new? Does he also ridicule her appearance for the same reason?