Ornn is no longer a problem in pro games after his last nerfs so those dont call for him to get nerfed.
He has the worst winrate of any toplaner and has low pick- and banrate. Ornn also isnt super hard to play or extremely team reliant to support him being OP with abysmal winrate(like azir or ryze).
There just are no good arguments to support the claim that Ornn is still OP in soloQ. I like the brittle nerf and moving his power away from early laning is ok, but for that to not be way too harsh he needs big buffs in other areas.
Ornn just isnt a balance problem in soloQ, some point the data is so overwhelming that calling a champ OP gets totally ridiculous.