How are you being punished?
If you perform good enough to be a Diamond, you will get there.
If you are only good enough to be a Onyx 3 80% or so, then that’s what you will be.
How is that a “bad system” ? It’s placing you where you are meant to be - as stated several times, you don’t get Diamond because you think you deserve it or that you just want it. You have to earn it.