Easiest to tackle is probably looks. To join app everyone would have to submit a set of basic pictures. Straight on headshot, full body shot, full profile shot, all in natural lighting. The community would then vote on the pictures. Absolute score would be meaningless, so each individual would be assigned a percentile score.

Then it'd look into education level and annual income. Men would match higher with women the made X% more than

Men would match higher with women they were a few years older than.

There are other traits that might be matched like on the Big 5 Personality scale.