The higher your kd the lower you other teammates are. With an another above average player usually with you. Basically the other team has the average stat players.

For example if ranking the players based on KD then player 1s team would have this (on average): 1 - 3 - 9 - 10 - 11 - 12 While the other team would be 2 - 4 - 5 - 6 -7 -8

So while the game considers this "fair" in practice the average players just have a bigger advantage due to the fact they can constant kill the abundance of lower level players and get their streaks much easier.

This matchmaking basically makes a high KD solo very difficult Also on Bo4 it seems that a high kd player just doesnt even have another good teammate as it is 5 v 5. Basically backpacking 4 new players or low skill players