The stats are poor.
I would even prefer Bosnich and Howard to Onana. Obviously different times, so those two wouldn’t be good in the modern game as goalkeeping has changed.
However, it’s hard to argue he’s not the worst no 1 we have had in the PL era. I am not going to count the likes of Tiabi or other keepers who weren’t a nailed on no 1.
When you look at Bosnich, Howard or Barthez (second season), when they has troubles, and it was clear it wasn’t going to work - they got binned off and replaced quickly. That’s exactly what we need to do with Onana (and the reality is it should have already happened - esp. after the CL last season).