I'm NOT trying to suggest that De Gea should've saved Antony's free-kick here before anyone chimes in but, just to give the other side here, I watched the highlights of Fiorentina-Betis and if you watch Antony's free-kick De Gea actually dives for it using
the same technique Onana did last night. (The goal is at around 0:40 in that clip?
As I say, I'm not trying to suggest De Gea should have saved Antony's free kick there (it was off the post), but more trying to labour the point that I think we're reaching the stage where any perceived mistake Onana makes is amplified to a ridiculous degree to make it out like no other top-level goalkeeper would ever make it.