Yeah I can agree with you on this. I also think Emiliano Martinez would have been a better choice as first choice goalkeeper for United because not will he make better saves, he will also command the defense around him with his leadership qualities, United missed a good player in Martinez.
Martinez is a very good and solid goalkeeper and most of us thought he was going to be transferred to Manchester United during the last days of the transfer window but we did not see that happen, best known to the Manchester United why they did not go for him. I know the management are aware Onana will not be there that he was going to leave for another club, why they didn't go for an experienced Martinez is still what is shocking me now.