Season rewards?
Right now, the only point of the rank system is to make the matches at least a bit more fair. Sometimes I feel like being in the high ranks feels more punishing than rewarding so what's the point of even trying to rank up? The achievements you get are alright but after you've unlocked them, there's no other rewards.
So my solution for this is simple: Give the players iridescent shards at the end of every season. The higher the rank, the more shards you get. Maybe somehow like this I guess?

The maximum amount of shards you can get could of course be more or less depending on people's opinion but I think it's wise to make it scale more towards the higher ranks.
Comments
Also I put the same rewards for both rank 1 and 2 because of how easy it is to drop from rank 1.