Threat tells you nothing about a plyers skill. (dethreaters, only 1 game can make the difference between gold and silver...) So theres only the Rank left to tell anything about your opponents strenght which is harder to manipulate (you could pledge to a max contect but would not unlock new stuff but you cant decrease your rank).
A high rank means high play time which is very important in this game so you know all the positions and how to engage enemies in that positions, you know which weapon to use in which situation, you have better weapon handling, access to more mods.....
To say that rank is not the best option to base the matchmaking on. But its by far the best option which is already in the game right now to get a decent matchmaking.
I often see a team of 2 or 3 max rank enemies versus my team with much lower guys (like me + R50 + R70 + R120 versus R255 + R255 + R220). It doesnt help us to have 1 more guy in the team and at the end the GOLDEN R120 will have max 1 or 2 kills because the max rank guys destroy the low ranks so hard. Or a match me + R255 versus 3x R60 none of this R60 guys had a kill.
In my opinion this is the reason why newer players quit or stop playing the game. Because they want to win games and get some kills too but this matchmaking system higly favors high rank players.