So you're happy to look at McCarthy's record from day one. Fair enough. By your own admission, playing 5 at the back has been a mistake.
So if it doesn't work, how many more attempts has McCarthy got to get it to work, based on his initial successes after he took over? If the answer is zero, then you can't be happy with MM playing 5 centre backs. Otherwise, you are happy for him to keep giving 5 centre backs a go.