Extremely broken ranking system

So at first this game seemed to have a pretty decent ranking system. But now I’m getting matched with onyx and diamond players even though I’m in platinum. And it’s not just a once in a while type thing, every game I get matched with diamond and every few games I see onyx players. It sucks cause I’m not very good at this game to begin with, but when I get matched with high tier diamond or onyx I get absolutely destroyed.

The ranking system is severely flawed. I took a look at the ranks for doubles, and there are 200 champions, and only 6 onyx. The rest are diamonds.