Trying to understand how the ranked system works.

After doing my placement matches this season I thought I went a fair 7/3. I wasn't expecting to go up after that, but I sure wasn't expecting to go down a whole 5 tiers from s1 gold promos to bottom of bronze 1. I'm not even writing this as if I'm upset or mad.. (okay maybe a little bit upset.) In all seriousness, how does it work, where does it make sense that I go positive in placements and end up worse off then last year. Positive k/d/a on all my champs, high kill participation. I'm really just lost as to how this even works, because to me, penalizing your players for playing good dosen't seem like a great marketing strategy. If that is the case then what is the point of even playing good in your placements knowing that you're going to go backwards no matter what after you go 10/10. If I could just get one person from Riot to just converse with me about this that would be amazing. I'm not really expecting that to happen, but who really knows.