Actually, I tested on the ninja matches in training and if I were to use random ninjas, I match more frequently to their "rarity". So matching someone who is running the genin characters, I used ninjas like moeji. I rarely match with people who strictly genin ninjas (i.e. very new players) if I don't do this trick. Of course this could have been coincidence but it happened to me several times so I don't know what exact what say.

As to your point, I do agree with you as people would try to abuse the system since people who has more ninjas can benefit the most than someone like OP. Since it seems like OP started playing almost 1 year, if you aren't a whale, it will take some time to do ranked competitively. Until then, you will be food for those can do ranked no problem. Just know the simple tricks of doing ranked: don't do it early in the month, know when to stop when you are losing and going into the negatives, know what time to do ranked, etc.