How can you quantify what is attractive and what isn't?

very easily, their system works on a 10 point rating system. Not only this, but even machines have been able to quantifiably rate people based on things like symmetry and ratios. Your problem here seems to be that you're saying opinions can't be ranked because there is no logical true or false to an opinion. However, opinions can be grouped into popular thought. I can say "people don't like eating shit", because if I asked everyone to eat shit, pretty much no one would. Is "shit tastes bad" a fundamental property of the boundary conditions of the universe? No. Does that have any relevance to the point? Also no.

But even ignoring that, physical attractiveness is literally a non-opinion based quantifiable property, attractiveness by definition is a measure of other members of the species wanting to mate with you. You can literally measure that very easily by asking the other members of the species.

you can't use dating profiles as a representative of a country

why

Not sure why you feel the need to get personal

because:

I wouldn't say that British people are hideous

then you objectively have low standards, backed up by statistics and health polls. Which is completely fine, date who you want to date, but you're fooling yourself if you think the people over here are attractive when it's been objectively shown to be false.