Honest feedback needed!!!!

I haven't played LoL for very long, mainly some of Season 4 and most of Season 5 I think. My MMR was low in Season 5 and I'd win a few games, gain 16 LP and then lose and lose 20 LP per loss. I felt like I was playing good enough but not being rewarded for my play. I quit playing LoL for a while.

I came back during the Season 6 preseason after LOTS of practice before playing ranked. Was excited to start my placements. I got out of B5 pretty quickly in preseason. So I go 7-3 in placements with a KDA of 11.2 / 5.4 / 9.1. I carried many of those games. Where do I get placed? Bronze 5. My MMR says it is 478 when average is 717. I've asked this before and people say "well just keep winning and it will balance out" and other things like that. I put time into this game, I try to improve constantly. Where is my incentive to even keep playing? I probably carry 75% of every Bronze game I play. Yet I have an atrocious MMR. No, I don't understand MMR and I personally think it's a f**king joke. What more do I have to do? And if you say just keep playing....well a person can only "keep playing" so long without getting discouraged. It's ranked, it's competitive. There has to be incentives for playing this game. Reward me for my good play. I'm not saying where I should be. I don't know where I should be. I just know that it's not Bronze 5.

Anyone have any logical, HELPFUL responses or explanations?