I assumed that comment had to do with fashion (or attractiveness).

It could be referring to race, but the fact that you "can't imagine" what else it could refer to says a lot about you and nothing at all about the original poster.

Because the only two characteristics Parisian people have are size and race?

The very Wikipedia article we happen to be discussing contains "...Renoux indicates that Japanese media, magazines in particular, often depict Paris as a place where most people on the street look like "stick-thin" models and most women dress in high fashion brands such as Louis Vuitton...".

And OP themselves excluded "size". So I guess they are upset that people don't dress up. A'right.

Are you familiar with the concept of euphemism and dog whistles? Please tell me what visual (since OP mentioned how Parisians "look") characteristic you presumed OP had in mind.

One of the big stereotypes of Paris is fashion and high society. My assumption was that he was saying people are dressed like slobs, that there's a lot of evidence of poverty, and people don't hold themselves in a manner someone with an idealistic view of Paris and Parisians would imagine.

Having been to Paris myself, all of these are true.

Duly addressed in my edit above.

Are you familiar with the concept of confirmation bias? Look hard enough for something and you'll see it ... whether it's there or not.