Age and progress on research into that age is the only factor that matters with hood merges.
If they've got a lot of points then it likely means they've either been playing for longer on a consistent basis or have been utilising the things that gather points more effectively. Ranking Points won't tell you anything about a city military attacking strength, military defensive strength, how well rounded the city is, if they have advanced troops available or how many plunder-able buildings the city has.
If hypothetically hood merges were based on those factors instead of age (or in addition to) you've then got a lot of debatable factors. How much worth does each of those factors have compared to each other? Would it be possible to prevent users from storing buildings to manipulate the hood merges and then put the buildings back? What if a player chooses to completely ignore one of those aspects? How do you determine where a no defence player should be placed? What about a player with huge defences but no attacking army stats? Should a player who chooses to handicap themselves by not utilising what's available be given an easier opponent? Or should only the most developed aspect of your city be used to determine placement? Should each ages units be given a different weighting towards hoods mergers? How would you determine the value of units in each age when combined with boosts? How do unique unit abilities/skills factor into that?
Then once you've answered those questions you've got another problem. Doing hood merges on that criteria would only give you a closer matchup if enough players would change position in the hood merges from what we have currently when basing it solely on age.