Make end of season rewards for your best highest, not where you end up at. That's anti-fun.
After playing this game since release, I've finally made it to gold. I made it up to gold 4, in my series to 3, and failed the series. I've now gone on a mega losing streak back down to gold 5, zero points. I've lost several games at zero points (on top of my now terrible hidden MMR, I'm sure).
I am actually considering quitting the game for the season so that I don't fall back down to silver and miss out on the rewards.
This is an anti-fun mechanic.