Ornn currently has the LOWEST winrate of all champions at 35%
https://euw.op.gg/statistics/champion/
https://euw.op.gg/champion/ornn/statistics/top
I think this is partly due to people buying his upgrades early on but I believe it's also due to the fact that his abilities are extremely telegraphed and there are other abilities (or champions) who can do the same as him but better. He also runs out of mana extremely quickly too.
I mean this might be another Ivern 2.0 where he's weak until people figure out how to play him but right now, I hardly doubt that's the case. In all honesty I could probably take anyone top and beat the guy in lane.
He's in need of some buffs or changes.
At least Ryze players can be glad they aren't playing the worst champion right now.